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   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   * This code is free software; you can redistribute it and/or modify it
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   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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  package java.lang.invoke;
  
  import java.lang.reflect.*;
  import java.nio.ByteOrder;
  import java.util.List;
  import java.util.Arrays;
  import java.util.ArrayList;
  import java.util.NoSuchElementException;
  
  import sun.invoke.util.VerifyAccess;
  import sun.invoke.util.Wrapper;
  import sun.reflect.Reflection;
  
  import static java.lang.invoke.MethodHandleStatics.*;
  
  /**
   * This class consists exclusively of static methods that operate on or return
   * method handles. They fall into several categories:
   * <ul>
   * <li>Lookup methods which help create method handles for methods and fields.
   * <li>Combinator methods, which combine or transform pre-existing method handles into new ones.
   * <li>Other factory methods to create method handles that emulate other common JVM operations or control flow patterns.
   * </ul>
   * <p>
   * @author John Rose, JSR 292 EG
   * @since 1.7
   */
  public class MethodHandles {
  
      private MethodHandles() { }  // do not instantiate
  
      // Android-changed: We do not use MemberName / MethodHandleImpl.
      //
      // private static final MemberName.Factory IMPL_NAMES = MemberName.getFactory();
      // static { MethodHandleImpl.initStatics(); }
      // See IMPL_LOOKUP below.
  
      //// Method handle creation from ordinary methods.
  
      /**
       * Returns a {@link Lookup lookup object} with
       * full capabilities to emulate all supported bytecode behaviors of the caller.
       * These capabilities include <a href="MethodHandles.Lookup.html#privacc">private access</a> to the caller.
       * Factory methods on the lookup object can create
       * <a href="MethodHandleInfo.html#directmh">direct method handles</a>
       * for any member that the caller has access to via bytecodes,
       * including protected and private fields and methods.
       * This lookup object is a <em>capability</em> which may be delegated to trusted agents.
       * Do not store it in place where untrusted code can access it.
       * <p>
       * This method is caller sensitive, which means that it may return different
       * values to different callers.
       * <p>
       * For any given caller class {@code C}, the lookup object returned by this call
       * has equivalent capabilities to any lookup object
       * supplied by the JVM to the bootstrap method of an
       * <a href="package-summary.html#indyinsn">invokedynamic instruction</a>
       * executing in the same caller class {@code C}.
       * @return a lookup object for the caller of this method, with private access
       */
      // Android-changed: Remove caller sensitive.
      // @CallerSensitive
      public static Lookup lookup() {
          return new Lookup(Reflection.getCallerClass());
      }
  
      /**
       * Returns a {@link Lookup lookup object} which is trusted minimally.
       * It can only be used to create method handles to
       * publicly accessible fields and methods.
       * <p>
       * As a matter of pure convention, the {@linkplain Lookup#lookupClass lookup class}
       * of this lookup object will be {@link Object}.
       *
       * <p style="font-size:smaller;">
       * <em>Discussion:</em>
       * The lookup class can be changed to any other class {@code C} using an expression of the form
       * {@link Lookup#in publicLookup().in(C.class)}.
       * Since all classes have equal access to public names,
       * such a change would confer no new access rights.
       * A public lookup object is always subject to
       * <a href="MethodHandles.Lookup.html#secmgr">security manager checks</a>.
       * Also, it cannot access
       * <a href="MethodHandles.Lookup.html#callsens">caller sensitive methods</a>.
       * @return a lookup object which is trusted minimally
       */
      public static Lookup publicLookup() {
          return Lookup.PUBLIC_LOOKUP;
      }
  
      /**
       * Performs an unchecked "crack" of a
       * <a href="MethodHandleInfo.html#directmh">direct method handle</a>.
       * The result is as if the user had obtained a lookup object capable enough
       * to crack the target method handle, called
       * {@link Lookup#revealDirect Lookup.revealDirect}
       * on the target to obtain its symbolic reference, and then called
       * {@link MethodHandleInfo#reflectAs MethodHandleInfo.reflectAs}
       * to resolve the symbolic reference to a member.
       * <p>
       * If there is a security manager, its {@code checkPermission} method
       * is called with a {@code ReflectPermission("suppressAccessChecks")} permission.
       * @param <T> the desired type of the result, either {@link Member} or a subtype
       * @param target a direct method handle to crack into symbolic reference components
       * @param expected a class object representing the desired result type {@code T}
       * @return a reference to the method, constructor, or field object
       * @exception SecurityException if the caller is not privileged to call {@code setAccessible}
       * @exception NullPointerException if either argument is {@code null}
       * @exception IllegalArgumentException if the target is not a direct method handle
       * @exception ClassCastException if the member is not of the expected type
       * @since 1.8
       */
      public static <T extends Member> T
      reflectAs(Class<T> expected, MethodHandle target) {
          MethodHandleImpl directTarget = getMethodHandleImpl(target);
          // Given that this is specified to be an "unchecked" crack, we can directly allocate
          // a member from the underlying ArtField / Method and bypass all associated access checks.
          return expected.cast(directTarget.getMemberInternal());
      }
  
      /**
       * A <em>lookup object</em> is a factory for creating method handles,
       * when the creation requires access checking.
       * Method handles do not perform
       * access checks when they are called, but rather when they are created.
       * Therefore, method handle access
       * restrictions must be enforced when a method handle is created.
       * The caller class against which those restrictions are enforced
       * is known as the {@linkplain #lookupClass lookup class}.
       * <p>
       * A lookup class which needs to create method handles will call
       * {@link #lookup MethodHandles.lookup} to create a factory for itself.
       * When the {@code Lookup} factory object is created, the identity of the lookup class is
       * determined, and securely stored in the {@code Lookup} object.
       * The lookup class (or its delegates) may then use factory methods
       * on the {@code Lookup} object to create method handles for access-checked members.
       * This includes all methods, constructors, and fields which are allowed to the lookup class,
       * even private ones.
       *
       * <h1><a name="lookups"></a>Lookup Factory Methods</h1>
       * The factory methods on a {@code Lookup} object correspond to all major
       * use cases for methods, constructors, and fields.
       * Each method handle created by a factory method is the functional
       * equivalent of a particular <em>bytecode behavior</em>.
       * (Bytecode behaviors are described in section 5.4.3.5 of the Java Virtual Machine Specification.)
       * Here is a summary of the correspondence between these factory methods and
       * the behavior the resulting method handles:
       * <table border=1 cellpadding=5 summary="lookup method behaviors">
       * <tr>
       *     <th><a name="equiv"></a>lookup expression</th>
       *     <th>member</th>
       *     <th>bytecode behavior</th>
       * </tr>
       * <tr>
       *     <td>{@link Lookup#findGetter lookup.findGetter(C.class,"f",FT.class)}</td>
       *     <td>{@code FT f;}</td><td>{@code (T) this.f;}</td>
       * </tr>
       * <tr>
       *     <td>{@link Lookup#findStaticGetter lookup.findStaticGetter(C.class,"f",FT.class)}</td>
       *     <td>{@code static}<br>{@code FT f;}</td><td>{@code (T) C.f;}</td>
       * </tr>
       * <tr>
       *     <td>{@link Lookup#findSetter lookup.findSetter(C.class,"f",FT.class)}</td>
       *     <td>{@code FT f;}</td><td>{@code this.f = x;}</td>
       * </tr>
       * <tr>
       *     <td>{@link Lookup#findStaticSetter lookup.findStaticSetter(C.class,"f",FT.class)}</td>
       *     <td>{@code static}<br>{@code FT f;}</td><td>{@code C.f = arg;}</td>
       * </tr>
       * <tr>
       *     <td>{@link Lookup#findVirtual lookup.findVirtual(C.class,"m",MT)}</td>
       *     <td>{@code T m(A*);}</td><td>{@code (T) this.m(arg*);}</td>
       * </tr>
       * <tr>
       *     <td>{@link Lookup#findStatic lookup.findStatic(C.class,"m",MT)}</td>
       *     <td>{@code static}<br>{@code T m(A*);}</td><td>{@code (T) C.m(arg*);}</td>
       * </tr>
       * <tr>
       *     <td>{@link Lookup#findSpecial lookup.findSpecial(C.class,"m",MT,this.class)}</td>
       *     <td>{@code T m(A*);}</td><td>{@code (T) super.m(arg*);}</td>
       * </tr>
       * <tr>
       *     <td>{@link Lookup#findConstructor lookup.findConstructor(C.class,MT)}</td>
       *     <td>{@code C(A*);}</td><td>{@code new C(arg*);}</td>
       * </tr>
       * <tr>
       *     <td>{@link Lookup#unreflectGetter lookup.unreflectGetter(aField)}</td>
       *     <td>({@code static})?<br>{@code FT f;}</td><td>{@code (FT) aField.get(thisOrNull);}</td>
       * </tr>
       * <tr>
       *     <td>{@link Lookup#unreflectSetter lookup.unreflectSetter(aField)}</td>
       *     <td>({@code static})?<br>{@code FT f;}</td><td>{@code aField.set(thisOrNull, arg);}</td>
       * </tr>
       * <tr>
       *     <td>{@link Lookup#unreflect lookup.unreflect(aMethod)}</td>
       *     <td>({@code static})?<br>{@code T m(A*);}</td><td>{@code (T) aMethod.invoke(thisOrNull, arg*);}</td>
       * </tr>
       * <tr>
       *     <td>{@link Lookup#unreflectConstructor lookup.unreflectConstructor(aConstructor)}</td>
       *     <td>{@code C(A*);}</td><td>{@code (C) aConstructor.newInstance(arg*);}</td>
       * </tr>
       * <tr>
       *     <td>{@link Lookup#unreflect lookup.unreflect(aMethod)}</td>
       *     <td>({@code static})?<br>{@code T m(A*);}</td><td>{@code (T) aMethod.invoke(thisOrNull, arg*);}</td>
       * </tr>
       * </table>
       *
       * Here, the type {@code C} is the class or interface being searched for a member,
       * documented as a parameter named {@code refc} in the lookup methods.
       * The method type {@code MT} is composed from the return type {@code T}
       * and the sequence of argument types {@code A*}.
       * The constructor also has a sequence of argument types {@code A*} and
       * is deemed to return the newly-created object of type {@code C}.
       * Both {@code MT} and the field type {@code FT} are documented as a parameter named {@code type}.
       * The formal parameter {@code this} stands for the self-reference of type {@code C};
       * if it is present, it is always the leading argument to the method handle invocation.
       * (In the case of some {@code protected} members, {@code this} may be
       * restricted in type to the lookup class; see below.)
       * The name {@code arg} stands for all the other method handle arguments.
       * In the code examples for the Core Reflection API, the name {@code thisOrNull}
       * stands for a null reference if the accessed method or field is static,
       * and {@code this} otherwise.
       * The names {@code aMethod}, {@code aField}, and {@code aConstructor} stand
       * for reflective objects corresponding to the given members.
       * <p>
       * In cases where the given member is of variable arity (i.e., a method or constructor)
       * the returned method handle will also be of {@linkplain MethodHandle#asVarargsCollector variable arity}.
       * In all other cases, the returned method handle will be of fixed arity.
       * <p style="font-size:smaller;">
       * <em>Discussion:</em>
       * The equivalence between looked-up method handles and underlying
       * class members and bytecode behaviors
       * can break down in a few ways:
       * <ul style="font-size:smaller;">
       * <li>If {@code C} is not symbolically accessible from the lookup class's loader,
       * the lookup can still succeed, even when there is no equivalent
       * Java expression or bytecoded constant.
       * <li>Likewise, if {@code T} or {@code MT}
       * is not symbolically accessible from the lookup class's loader,
       * the lookup can still succeed.
       * For example, lookups for {@code MethodHandle.invokeExact} and
       * {@code MethodHandle.invoke} will always succeed, regardless of requested type.
       * <li>If there is a security manager installed, it can forbid the lookup
       * on various grounds (<a href="MethodHandles.Lookup.html#secmgr">see below</a>).
       * By contrast, the {@code ldc} instruction on a {@code CONSTANT_MethodHandle}
       * constant is not subject to security manager checks.
       * <li>If the looked-up method has a
       * <a href="MethodHandle.html#maxarity">very large arity</a>,
       * the method handle creation may fail, due to the method handle
       * type having too many parameters.
       * </ul>
       *
       * <h1><a name="access"></a>Access checking</h1>
       * Access checks are applied in the factory methods of {@code Lookup},
       * when a method handle is created.
       * This is a key difference from the Core Reflection API, since
       * {@link Method#invoke java.lang.reflect.Method.invoke}
       * performs access checking against every caller, on every call.
       * <p>
       * All access checks start from a {@code Lookup} object, which
       * compares its recorded lookup class against all requests to
       * create method handles.
       * A single {@code Lookup} object can be used to create any number
       * of access-checked method handles, all checked against a single
       * lookup class.
       * <p>
       * A {@code Lookup} object can be shared with other trusted code,
       * such as a metaobject protocol.
       * A shared {@code Lookup} object delegates the capability
       * to create method handles on private members of the lookup class.
       * Even if privileged code uses the {@code Lookup} object,
       * the access checking is confined to the privileges of the
       * original lookup class.
       * <p>
       * A lookup can fail, because
       * the containing class is not accessible to the lookup class, or
       * because the desired class member is missing, or because the
       * desired class member is not accessible to the lookup class, or
       * because the lookup object is not trusted enough to access the member.
       * In any of these cases, a {@code ReflectiveOperationException} will be
       * thrown from the attempted lookup.  The exact class will be one of
       * the following:
       * <ul>
       * <li>NoSuchMethodException &mdash; if a method is requested but does not exist
       * <li>NoSuchFieldException &mdash; if a field is requested but does not exist
       * <li>IllegalAccessException &mdash; if the member exists but an access check fails
       * </ul>
       * <p>
       * In general, the conditions under which a method handle may be
       * looked up for a method {@code M} are no more restrictive than the conditions
       * under which the lookup class could have compiled, verified, and resolved a call to {@code M}.
       * Where the JVM would raise exceptions like {@code NoSuchMethodError},
       * a method handle lookup will generally raise a corresponding
       * checked exception, such as {@code NoSuchMethodException}.
       * And the effect of invoking the method handle resulting from the lookup
       * is <a href="MethodHandles.Lookup.html#equiv">exactly equivalent</a>
       * to executing the compiled, verified, and resolved call to {@code M}.
       * The same point is true of fields and constructors.
       * <p style="font-size:smaller;">
       * <em>Discussion:</em>
       * Access checks only apply to named and reflected methods,
       * constructors, and fields.
       * Other method handle creation methods, such as
       * {@link MethodHandle#asType MethodHandle.asType},
       * do not require any access checks, and are used
       * independently of any {@code Lookup} object.
       * <p>
       * If the desired member is {@code protected}, the usual JVM rules apply,
       * including the requirement that the lookup class must be either be in the
       * same package as the desired member, or must inherit that member.
       * (See the Java Virtual Machine Specification, sections 4.9.2, 5.4.3.5, and 6.4.)
       * In addition, if the desired member is a non-static field or method
       * in a different package, the resulting method handle may only be applied
       * to objects of the lookup class or one of its subclasses.
       * This requirement is enforced by narrowing the type of the leading
       * {@code this} parameter from {@code C}
       * (which will necessarily be a superclass of the lookup class)
       * to the lookup class itself.
       * <p>
       * The JVM imposes a similar requirement on {@code invokespecial} instruction,
       * that the receiver argument must match both the resolved method <em>and</em>
       * the current class.  Again, this requirement is enforced by narrowing the
       * type of the leading parameter to the resulting method handle.
       * (See the Java Virtual Machine Specification, section 4.10.1.9.)
       * <p>
       * The JVM represents constructors and static initializer blocks as internal methods
       * with special names ({@code "<init>"} and {@code "<clinit>"}).
       * The internal syntax of invocation instructions allows them to refer to such internal
       * methods as if they were normal methods, but the JVM bytecode verifier rejects them.
       * A lookup of such an internal method will produce a {@code NoSuchMethodException}.
       * <p>
       * In some cases, access between nested classes is obtained by the Java compiler by creating
       * an wrapper method to access a private method of another class
       * in the same top-level declaration.
       * For example, a nested class {@code C.D}
       * can access private members within other related classes such as
       * {@code C}, {@code C.D.E}, or {@code C.B},
       * but the Java compiler may need to generate wrapper methods in
       * those related classes.  In such cases, a {@code Lookup} object on
       * {@code C.E} would be unable to those private members.
       * A workaround for this limitation is the {@link Lookup#in Lookup.in} method,
       * which can transform a lookup on {@code C.E} into one on any of those other
       * classes, without special elevation of privilege.
       * <p>
       * The accesses permitted to a given lookup object may be limited,
       * according to its set of {@link #lookupModes lookupModes},
       * to a subset of members normally accessible to the lookup class.
       * For example, the {@link #publicLookup publicLookup}
       * method produces a lookup object which is only allowed to access
       * public members in public classes.
       * The caller sensitive method {@link #lookup lookup}
       * produces a lookup object with full capabilities relative to
       * its caller class, to emulate all supported bytecode behaviors.
       * Also, the {@link Lookup#in Lookup.in} method may produce a lookup object
       * with fewer access modes than the original lookup object.
       *
       * <p style="font-size:smaller;">
       * <a name="privacc"></a>
       * <em>Discussion of private access:</em>
       * We say that a lookup has <em>private access</em>
       * if its {@linkplain #lookupModes lookup modes}
       * include the possibility of accessing {@code private} members.
       * As documented in the relevant methods elsewhere,
       * only lookups with private access possess the following capabilities:
       * <ul style="font-size:smaller;">
       * <li>access private fields, methods, and constructors of the lookup class
       * <li>create method handles which invoke <a href="MethodHandles.Lookup.html#callsens">caller sensitive</a> methods,
       *     such as {@code Class.forName}
       * <li>create method handles which {@link Lookup#findSpecial emulate invokespecial} instructions
       * <li>avoid <a href="MethodHandles.Lookup.html#secmgr">package access checks</a>
       *     for classes accessible to the lookup class
       * <li>create {@link Lookup#in delegated lookup objects} which have private access to other classes
       *     within the same package member
       * </ul>
       * <p style="font-size:smaller;">
       * Each of these permissions is a consequence of the fact that a lookup object
       * with private access can be securely traced back to an originating class,
       * whose <a href="MethodHandles.Lookup.html#equiv">bytecode behaviors</a> and Java language access permissions
       * can be reliably determined and emulated by method handles.
       *
       * <h1><a name="secmgr"></a>Security manager interactions</h1>
       * Although bytecode instructions can only refer to classes in
       * a related class loader, this API can search for methods in any
       * class, as long as a reference to its {@code Class} object is
       * available.  Such cross-loader references are also possible with the
       * Core Reflection API, and are impossible to bytecode instructions
       * such as {@code invokestatic} or {@code getfield}.
       * There is a {@linkplain SecurityManager security manager API}
       * to allow applications to check such cross-loader references.
       * These checks apply to both the {@code MethodHandles.Lookup} API
       * and the Core Reflection API
       * (as found on {@link Class Class}).
       * <p>
       * If a security manager is present, member lookups are subject to
       * additional checks.
       * From one to three calls are made to the security manager.
       * Any of these calls can refuse access by throwing a
       * {@link SecurityException SecurityException}.
       * Define {@code smgr} as the security manager,
       * {@code lookc} as the lookup class of the current lookup object,
       * {@code refc} as the containing class in which the member
       * is being sought, and {@code defc} as the class in which the
       * member is actually defined.
       * The value {@code lookc} is defined as <em>not present</em>
       * if the current lookup object does not have
       * <a href="MethodHandles.Lookup.html#privacc">private access</a>.
       * The calls are made according to the following rules:
       * <ul>
       * <li><b>Step 1:</b>
       *     If {@code lookc} is not present, or if its class loader is not
       *     the same as or an ancestor of the class loader of {@code refc},
       *     then {@link SecurityManager#checkPackageAccess
       *     smgr.checkPackageAccess(refcPkg)} is called,
       *     where {@code refcPkg} is the package of {@code refc}.
       * <li><b>Step 2:</b>
       *     If the retrieved member is not public and
       *     {@code lookc} is not present, then
       *     {@link SecurityManager#checkPermission smgr.checkPermission}
       *     with {@code RuntimePermission("accessDeclaredMembers")} is called.
       * <li><b>Step 3:</b>
       *     If the retrieved member is not public,
       *     and if {@code lookc} is not present,
       *     and if {@code defc} and {@code refc} are different,
       *     then {@link SecurityManager#checkPackageAccess
       *     smgr.checkPackageAccess(defcPkg)} is called,
       *     where {@code defcPkg} is the package of {@code defc}.
       * </ul>
       * Security checks are performed after other access checks have passed.
       * Therefore, the above rules presuppose a member that is public,
       * or else that is being accessed from a lookup class that has
       * rights to access the member.
       *
       * <h1><a name="callsens"></a>Caller sensitive methods</h1>
       * A small number of Java methods have a special property called caller sensitivity.
       * A <em>caller-sensitive</em> method can behave differently depending on the
       * identity of its immediate caller.
       * <p>
       * If a method handle for a caller-sensitive method is requested,
       * the general rules for <a href="MethodHandles.Lookup.html#equiv">bytecode behaviors</a> apply,
       * but they take account of the lookup class in a special way.
       * The resulting method handle behaves as if it were called
       * from an instruction contained in the lookup class,
       * so that the caller-sensitive method detects the lookup class.
       * (By contrast, the invoker of the method handle is disregarded.)
       * Thus, in the case of caller-sensitive methods,
       * different lookup classes may give rise to
       * differently behaving method handles.
       * <p>
       * In cases where the lookup object is
       * {@link #publicLookup publicLookup()},
       * or some other lookup object without
       * <a href="MethodHandles.Lookup.html#privacc">private access</a>,
       * the lookup class is disregarded.
       * In such cases, no caller-sensitive method handle can be created,
       * access is forbidden, and the lookup fails with an
       * {@code IllegalAccessException}.
       * <p style="font-size:smaller;">
       * <em>Discussion:</em>
       * For example, the caller-sensitive method
       * {@link Class#forName(String) Class.forName(x)}
       * can return varying classes or throw varying exceptions,
       * depending on the class loader of the class that calls it.
       * A public lookup of {@code Class.forName} will fail, because
       * there is no reasonable way to determine its bytecode behavior.
       * <p style="font-size:smaller;">
       * If an application caches method handles for broad sharing,
       * it should use {@code publicLookup()} to create them.
       * If there is a lookup of {@code Class.forName}, it will fail,
       * and the application must take appropriate action in that case.
       * It may be that a later lookup, perhaps during the invocation of a
       * bootstrap method, can incorporate the specific identity
       * of the caller, making the method accessible.
       * <p style="font-size:smaller;">
       * The function {@code MethodHandles.lookup} is caller sensitive
       * so that there can be a secure foundation for lookups.
       * Nearly all other methods in the JSR 292 API rely on lookup
       * objects to check access requests.
       */
      // Android-changed: Change link targets from MethodHandles#[public]Lookup to
      // #[public]Lookup to work around complaints from javadoc.
      public static final
      class Lookup {
          /** The class on behalf of whom the lookup is being performed. */
          /* @NonNull */ private final Class<?> lookupClass;
  
          /** The allowed sorts of members which may be looked up (PUBLIC, etc.). */
          private final int allowedModes;
  
          /** A single-bit mask representing {@code public} access,
           *  which may contribute to the result of {@link #lookupModes lookupModes}.
           *  The value, {@code 0x01}, happens to be the same as the value of the
           *  {@code public} {@linkplain Modifier#PUBLIC modifier bit}.
           */
          public static final int PUBLIC = Modifier.PUBLIC;
  
          /** A single-bit mask representing {@code private} access,
           *  which may contribute to the result of {@link #lookupModes lookupModes}.
           *  The value, {@code 0x02}, happens to be the same as the value of the
           *  {@code private} {@linkplain Modifier#PRIVATE modifier bit}.
           */
          public static final int PRIVATE = Modifier.PRIVATE;
  
          /** A single-bit mask representing {@code protected} access,
           *  which may contribute to the result of {@link #lookupModes lookupModes}.
           *  The value, {@code 0x04}, happens to be the same as the value of the
           *  {@code protected} {@linkplain Modifier#PROTECTED modifier bit}.
           */
          public static final int PROTECTED = Modifier.PROTECTED;
  
          /** A single-bit mask representing {@code package} access (default access),
           *  which may contribute to the result of {@link #lookupModes lookupModes}.
           *  The value is {@code 0x08}, which does not correspond meaningfully to
           *  any particular {@linkplain Modifier modifier bit}.
           */
          public static final int PACKAGE = Modifier.STATIC;
  
          private static final int ALL_MODES = (PUBLIC | PRIVATE | PROTECTED | PACKAGE);
  
          // Android-note: Android has no notion of a trusted lookup. If required, such lookups
          // are performed by the runtime. As a result, we always use lookupClass, which will always
          // be non-null in our implementation.
          //
          // private static final int TRUSTED   = -1;
  
          private static int fixmods(int mods) {
              mods &= (ALL_MODES - PACKAGE);
              return (mods != 0) ? mods : PACKAGE;
          }
  
          /** Tells which class is performing the lookup.  It is this class against
           *  which checks are performed for visibility and access permissions.
           *  <p>
           *  The class implies a maximum level of access permission,
           *  but the permissions may be additionally limited by the bitmask
           *  {@link #lookupModes lookupModes}, which controls whether non-public members
           *  can be accessed.
           *  @return the lookup class, on behalf of which this lookup object finds members
           */
          public Class<?> lookupClass() {
              return lookupClass;
          }
  
          /** Tells which access-protection classes of members this lookup object can produce.
           *  The result is a bit-mask of the bits
           *  {@linkplain #PUBLIC PUBLIC (0x01)},
           *  {@linkplain #PRIVATE PRIVATE (0x02)},
           *  {@linkplain #PROTECTED PROTECTED (0x04)},
           *  and {@linkplain #PACKAGE PACKAGE (0x08)}.
           *  <p>
           *  A freshly-created lookup object
           *  on the {@linkplain MethodHandles#lookup() caller's class}
           *  has all possible bits set, since the caller class can access all its own members.
           *  A lookup object on a new lookup class
           *  {@linkplain Lookup#in created from a previous lookup object}
           *  may have some mode bits set to zero.
           *  The purpose of this is to restrict access via the new lookup object,
           *  so that it can access only names which can be reached by the original
           *  lookup object, and also by the new lookup class.
           *  @return the lookup modes, which limit the kinds of access performed by this lookup object
           */
          public int lookupModes() {
              return allowedModes & ALL_MODES;
          }
  
          /** Embody the current class (the lookupClass) as a lookup class
           * for method handle creation.
           * Must be called by from a method in this package,
           * which in turn is called by a method not in this package.
           */
          Lookup(Class<?> lookupClass) {
              this(lookupClass, ALL_MODES);
              // make sure we haven't accidentally picked up a privileged class:
              checkUnprivilegedlookupClass(lookupClass, ALL_MODES);
          }
  
          private Lookup(Class<?> lookupClass, int allowedModes) {
              this.lookupClass = lookupClass;
              this.allowedModes = allowedModes;
          }
  
          /**
           * Creates a lookup on the specified new lookup class.
           * The resulting object will report the specified
           * class as its own {@link #lookupClass lookupClass}.
           * <p>
           * However, the resulting {@code Lookup} object is guaranteed
           * to have no more access capabilities than the original.
           * In particular, access capabilities can be lost as follows:<ul>
           * <li>If the new lookup class differs from the old one,
           * protected members will not be accessible by virtue of inheritance.
           * (Protected members may continue to be accessible because of package sharing.)
           * <li>If the new lookup class is in a different package
           * than the old one, protected and default (package) members will not be accessible.
           * <li>If the new lookup class is not within the same package member
           * as the old one, private members will not be accessible.
           * <li>If the new lookup class is not accessible to the old lookup class,
           * then no members, not even public members, will be accessible.
           * (In all other cases, public members will continue to be accessible.)
           * </ul>
           *
           * @param requestedLookupClass the desired lookup class for the new lookup object
           * @return a lookup object which reports the desired lookup class
           * @throws NullPointerException if the argument is null
           */
          public Lookup in(Class<?> requestedLookupClass) {
              requestedLookupClass.getClass();  // null check
              // Android-changed: There's no notion of a trusted lookup.
              // if (allowedModes == TRUSTED)  // IMPL_LOOKUP can make any lookup at all
              //    return new Lookup(requestedLookupClass, ALL_MODES);
  
              if (requestedLookupClass == this.lookupClass)
                  return this;  // keep same capabilities
              int newModes = (allowedModes & (ALL_MODES & ~PROTECTED));
              if ((newModes & PACKAGE) != 0
                  && !VerifyAccess.isSamePackage(this.lookupClass, requestedLookupClass)) {
                  newModes &= ~(PACKAGE|PRIVATE);
              }
              // Allow nestmate lookups to be created without special privilege:
              if ((newModes & PRIVATE) != 0
                  && !VerifyAccess.isSamePackageMember(this.lookupClass, requestedLookupClass)) {
                  newModes &= ~PRIVATE;
              }
              if ((newModes & PUBLIC) != 0
                  && !VerifyAccess.isClassAccessible(requestedLookupClass, this.lookupClass, allowedModes)) {
                  // The requested class it not accessible from the lookup class.
                  // No permissions.
                  newModes = 0;
              }
              checkUnprivilegedlookupClass(requestedLookupClass, newModes);
              return new Lookup(requestedLookupClass, newModes);
          }
  
          // Make sure outer class is initialized first.
          //
          // Android-changed: Removed unnecessary reference to IMPL_NAMES.
          // static { IMPL_NAMES.getClass(); }
  
          /** Version of lookup which is trusted minimally.
           *  It can only be used to create method handles to
           *  publicly accessible members.
           */
          static final Lookup PUBLIC_LOOKUP = new Lookup(Object.class, PUBLIC);
  
          /** Package-private version of lookup which is trusted. */
          static final Lookup IMPL_LOOKUP = new Lookup(Object.class, ALL_MODES);
  
          private static void checkUnprivilegedlookupClass(Class<?> lookupClass, int allowedModes) {
              String name = lookupClass.getName();
              if (name.startsWith("java.lang.invoke."))
                  throw newIllegalArgumentException("illegal lookupClass: "+lookupClass);
  
              // For caller-sensitive MethodHandles.lookup()
              // disallow lookup more restricted packages
              //
              // Android-changed: The bootstrap classloader isn't null.
              if (allowedModes == ALL_MODES &&
                      lookupClass.getClassLoader() == Object.class.getClassLoader()) {
                  if (name.startsWith("java.") ||
                          (name.startsWith("sun.")
                                  && !name.startsWith("sun.invoke.")
                                  && !name.equals("sun.reflect.ReflectionFactory"))) {
                      throw newIllegalArgumentException("illegal lookupClass: " + lookupClass);
                  }
              }
          }
  
          /**
           * Displays the name of the class from which lookups are to be made.
           * (The name is the one reported by {@link Class#getName() Class.getName}.)
           * If there are restrictions on the access permitted to this lookup,
           * this is indicated by adding a suffix to the class name, consisting
           * of a slash and a keyword.  The keyword represents the strongest
           * allowed access, and is chosen as follows:
           * <ul>
           * <li>If no access is allowed, the suffix is "/noaccess".
           * <li>If only public access is allowed, the suffix is "/public".
           * <li>If only public and package access are allowed, the suffix is "/package".
           * <li>If only public, package, and private access are allowed, the suffix is "/private".
           * </ul>
           * If none of the above cases apply, it is the case that full
           * access (public, package, private, and protected) is allowed.
           * In this case, no suffix is added.
           * This is true only of an object obtained originally from
           * {@link MethodHandles#lookup MethodHandles.lookup}.
           * Objects created by {@link Lookup#in Lookup.in}
           * always have restricted access, and will display a suffix.
           * <p>
           * (It may seem strange that protected access should be
           * stronger than private access.  Viewed independently from
           * package access, protected access is the first to be lost,
           * because it requires a direct subclass relationship between
           * caller and callee.)
           * @see #in
           */
          @Override
          public String toString() {
              String cname = lookupClass.getName();
              switch (allowedModes) {
              case 0:  // no privileges
                  return cname + "/noaccess";
              case PUBLIC:
                  return cname + "/public";
              case PUBLIC|PACKAGE:
                  return cname + "/package";
              case ALL_MODES & ~PROTECTED:
                  return cname + "/private";
              case ALL_MODES:
                  return cname;
              // Android-changed: No support for TRUSTED callers.
              // case TRUSTED:
              //    return "/trusted";  // internal only; not exported
              default:  // Should not happen, but it's a bitfield...
                  cname = cname + "/" + Integer.toHexString(allowedModes);
                  assert(false) : cname;
                  return cname;
              }
          }
  
          /**
           * Produces a method handle for a static method.
           * The type of the method handle will be that of the method.
           * (Since static methods do not take receivers, there is no
           * additional receiver argument inserted into the method handle type,
           * as there would be with {@link #findVirtual findVirtual} or {@link #findSpecial findSpecial}.)
           * The method and all its argument types must be accessible to the lookup object.
           * <p>
           * The returned method handle will have
           * {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
           * the method's variable arity modifier bit ({@code 0x0080}) is set.
           * <p>
           * If the returned method handle is invoked, the method's class will
           * be initialized, if it has not already been initialized.
           * <p><b>Example:</b>
           * <blockquote><pre>{@code
  import static java.lang.invoke.MethodHandles.*;
  import static java.lang.invoke.MethodType.*;
  ...
  MethodHandle MH_asList = publicLookup().findStatic(Arrays.class,
    "asList", methodType(List.class, Object[].class));
  assertEquals("[x, y]", MH_asList.invoke("x", "y").toString());
           * }</pre></blockquote>
           * @param refc the class from which the method is accessed
           * @param name the name of the method
           * @param type the type of the method
           * @return the desired method handle
           * @throws NoSuchMethodException if the method does not exist
           * @throws IllegalAccessException if access checking fails,
           *                                or if the method is not {@code static},
           *                                or if the method's variable arity modifier bit
           *                                is set and {@code asVarargsCollector} fails
           * @exception SecurityException if a security manager is present and it
           *                              <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
           * @throws NullPointerException if any argument is null
           */
          public
          MethodHandle findStatic(Class<?> refc, String name, MethodType type) throws NoSuchMethodException, IllegalAccessException {
              Method method = refc.getDeclaredMethod(name, type.ptypes());
              final int modifiers = method.getModifiers();
              if (!Modifier.isStatic(modifiers)) {
                  throw new IllegalAccessException("Method" + method + " is not static");
              }
              checkReturnType(method, type);
              checkAccess(refc, method.getDeclaringClass(), modifiers, method.getName());
              return createMethodHandle(method, MethodHandle.INVOKE_STATIC, type);
          }
  
          private MethodHandle findVirtualForMH(String name, MethodType type) {
              // these names require special lookups because of the implicit MethodType argument
              if ("invoke".equals(name))
                  return invoker(type);
              if ("invokeExact".equals(name))
                  return exactInvoker(type);
              return null;
          }
  
          private MethodHandle findVirtualForVH(String name, MethodType type) {
              VarHandle.AccessMode accessMode;
              try {
                  accessMode = VarHandle.AccessMode.valueFromMethodName(name);
              } catch (IllegalArgumentException e) {
                  return null;
              }
              return varHandleInvoker(accessMode, type);
          }
  
          private static MethodHandle createMethodHandle(Method method, int handleKind,
                                                         MethodType methodType) {
              MethodHandle mh = new MethodHandleImpl(method.getArtMethod(), handleKind, methodType);
              if (method.isVarArgs()) {
                  return new Transformers.VarargsCollector(mh);
              } else {
                  return mh;
              }
          }
  
          /**
           * Produces a method handle for a virtual method.
           * The type of the method handle will be that of the method,
           * with the receiver type (usually {@code refc}) prepended.
           * The method and all its argument types must be accessible to the lookup object.
           * <p>
           * When called, the handle will treat the first argument as a receiver
           * and dispatch on the receiver's type to determine which method
           * implementation to enter.
           * (The dispatching action is identical with that performed by an
           * {@code invokevirtual} or {@code invokeinterface} instruction.)
           * <p>
           * The first argument will be of type {@code refc} if the lookup
           * class has full privileges to access the member.  Otherwise
           * the member must be {@code protected} and the first argument
           * will be restricted in type to the lookup class.
           * <p>
           * The returned method handle will have
           * {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
           * the method's variable arity modifier bit ({@code 0x0080}) is set.
           * <p>
           * Because of the general <a href="MethodHandles.Lookup.html#equiv">equivalence</a> between {@code invokevirtual}
           * instructions and method handles produced by {@code findVirtual},
           * if the class is {@code MethodHandle} and the name string is
           * {@code invokeExact} or {@code invoke}, the resulting
           * method handle is equivalent to one produced by
           * {@link MethodHandles#exactInvoker MethodHandles.exactInvoker} or
           * {@link MethodHandles#invoker MethodHandles.invoker}
           * with the same {@code type} argument.
           *
           * <b>Example:</b>
           * <blockquote><pre>{@code
  import static java.lang.invoke.MethodHandles.*;
  import static java.lang.invoke.MethodType.*;
  ...
  MethodHandle MH_concat = publicLookup().findVirtual(String.class,
    "concat", methodType(String.class, String.class));
  MethodHandle MH_hashCode = publicLookup().findVirtual(Object.class,
    "hashCode", methodType(int.class));
  MethodHandle MH_hashCode_String = publicLookup().findVirtual(String.class,
    "hashCode", methodType(int.class));
  assertEquals("xy", (String) MH_concat.invokeExact("x", "y"));
  assertEquals("xy".hashCode(), (int) MH_hashCode.invokeExact((Object)"xy"));
  assertEquals("xy".hashCode(), (int) MH_hashCode_String.invokeExact("xy"));
  // interface method:
  MethodHandle MH_subSequence = publicLookup().findVirtual(CharSequence.class,
    "subSequence", methodType(CharSequence.class, int.class, int.class));
  assertEquals("def", MH_subSequence.invoke("abcdefghi", 3, 6).toString());
  // constructor "internal method" must be accessed differently:
  MethodType MT_newString = methodType(void.class); //()V for new String()
  try { assertEquals("impossible", lookup()
          .findVirtual(String.class, "<init>", MT_newString));
   } catch (NoSuchMethodException ex) { } // OK
  MethodHandle MH_newString = publicLookup()
    .findConstructor(String.class, MT_newString);
  assertEquals("", (String) MH_newString.invokeExact());
           * }</pre></blockquote>
           *
           * @param refc the class or interface from which the method is accessed
           * @param name the name of the method
           * @param type the type of the method, with the receiver argument omitted
           * @return the desired method handle
           * @throws NoSuchMethodException if the method does not exist
           * @throws IllegalAccessException if access checking fails,
           *                                or if the method is {@code static}
           *                                or if the method's variable arity modifier bit
           *                                is set and {@code asVarargsCollector} fails
           * @exception SecurityException if a security manager is present and it
           *                              <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
           * @throws NullPointerException if any argument is null
           */
          public MethodHandle findVirtual(Class<?> refc, String name, MethodType type) throws NoSuchMethodException, IllegalAccessException {
              // Special case : when we're looking up a virtual method on the MethodHandles class
              // itself, we can return one of our specialized invokers.
              if (refc == MethodHandle.class) {
                  MethodHandle mh = findVirtualForMH(name, type);
                  if (mh != null) {
                      return mh;
                  }
              } else if (refc == VarHandle.class) {
                  // Returns an non-exact invoker.
                  MethodHandle mh = findVirtualForVH(name, type);
                  if (mh != null) {
                      return mh;
                  }
              }
  
              Method method = refc.getInstanceMethod(name, type.ptypes());
              if (method == null) {
                  // This is pretty ugly and a consequence of the MethodHandles API. We have to throw
                  // an IAE and not an NSME if the method exists but is static (even though the RI's
                  // IAE has a message that says "no such method"). We confine the ugliness and
                  // slowness to the failure case, and allow getInstanceMethod to remain fairly
                  // general.
                  try {
                      Method m = refc.getDeclaredMethod(name, type.ptypes());
                      if (Modifier.isStatic(m.getModifiers())) {
                          throw new IllegalAccessException("Method" + m + " is static");
                      }
                  } catch (NoSuchMethodException ignored) {
                  }
  
                  throw new NoSuchMethodException(name + " "  + Arrays.toString(type.ptypes()));
              }
              checkReturnType(method, type);
  
              // We have a valid method, perform access checks.
              checkAccess(refc, method.getDeclaringClass(), method.getModifiers(), method.getName());
  
              // Insert the leading reference parameter.
              MethodType handleType = type.insertParameterTypes(0, refc);
              return createMethodHandle(method, MethodHandle.INVOKE_VIRTUAL, handleType);
          }
  
          /**
           * Produces a method handle which creates an object and initializes it, using
           * the constructor of the specified type.
           * The parameter types of the method handle will be those of the constructor,
           * while the return type will be a reference to the constructor's class.
           * The constructor and all its argument types must be accessible to the lookup object.
           * <p>
           * The requested type must have a return type of {@code void}.
           * (This is consistent with the JVM's treatment of constructor type descriptors.)
           * <p>
           * The returned method handle will have
           * {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
           * the constructor's variable arity modifier bit ({@code 0x0080}) is set.
           * <p>
           * If the returned method handle is invoked, the constructor's class will
           * be initialized, if it has not already been initialized.
           * <p><b>Example:</b>
           * <blockquote><pre>{@code
  import static java.lang.invoke.MethodHandles.*;
  import static java.lang.invoke.MethodType.*;
  ...
  MethodHandle MH_newArrayList = publicLookup().findConstructor(
    ArrayList.class, methodType(void.class, Collection.class));
  Collection orig = Arrays.asList("x", "y");
  Collection copy = (ArrayList) MH_newArrayList.invokeExact(orig);
  assert(orig != copy);
  assertEquals(orig, copy);
  // a variable-arity constructor:
  MethodHandle MH_newProcessBuilder = publicLookup().findConstructor(
    ProcessBuilder.class, methodType(void.class, String[].class));
  ProcessBuilder pb = (ProcessBuilder)
    MH_newProcessBuilder.invoke("x", "y", "z");
  assertEquals("[x, y, z]", pb.command().toString());
           * }</pre></blockquote>
           * @param refc the class or interface from which the method is accessed
           * @param type the type of the method, with the receiver argument omitted, and a void return type
           * @return the desired method handle
           * @throws NoSuchMethodException if the constructor does not exist
           * @throws IllegalAccessException if access checking fails
           *                                or if the method's variable arity modifier bit
           *                                is set and {@code asVarargsCollector} fails
           * @exception SecurityException if a security manager is present and it
           *                              <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
           * @throws NullPointerException if any argument is null
           */
          public MethodHandle findConstructor(Class<?> refc, MethodType type) throws NoSuchMethodException, IllegalAccessException {
              if (refc.isArray()) {
                  throw new NoSuchMethodException("no constructor for array class: " + refc.getName());
              }
              // The queried |type| is (PT1,PT2,..)V
              Constructor constructor = refc.getDeclaredConstructor(type.ptypes());
              if (constructor == null) {
                  throw new NoSuchMethodException(
                      "No constructor for " + constructor.getDeclaringClass() + " matching " + type);
              }
              checkAccess(refc, constructor.getDeclaringClass(), constructor.getModifiers(),
                      constructor.getName());
  
              return createMethodHandleForConstructor(constructor);
          }
  
          private MethodHandle createMethodHandleForConstructor(Constructor constructor) {
              Class<?> refc = constructor.getDeclaringClass();
              MethodType constructorType =
                      MethodType.methodType(refc, constructor.getParameterTypes());
              MethodHandle mh;
              if (refc == String.class) {
                  // String constructors have optimized StringFactory methods
                  // that matches returned type. These factory methods combine the
                  // memory allocation and initialization calls for String objects.
                  mh = new MethodHandleImpl(constructor.getArtMethod(), MethodHandle.INVOKE_DIRECT,
                                            constructorType);
              } else {
                  // Constructors for all other classes use a Construct transformer to perform
                  // their memory allocation and call to <init>.
                  MethodType initType = initMethodType(constructorType);
                  MethodHandle initHandle = new MethodHandleImpl(
                      constructor.getArtMethod(), MethodHandle.INVOKE_DIRECT, initType);
                  mh = new Transformers.Construct(initHandle, constructorType);
              }
  
              if (constructor.isVarArgs()) {
                  mh = new Transformers.VarargsCollector(mh);
              }
              return mh;
          }
  
          private static MethodType initMethodType(MethodType constructorType) {
              // Returns a MethodType appropriate for class <init>
              // methods. Constructor MethodTypes have the form
              // (PT1,PT2,...)C and class <init> MethodTypes have the
              // form (C,PT1,PT2,...)V.
              assert constructorType.rtype() != void.class;
  
              // Insert constructorType C as the first parameter type in
              // the MethodType for <init>.
              Class<?> [] initPtypes = new Class<?> [constructorType.ptypes().length + 1];
              initPtypes[0] = constructorType.rtype();
              System.arraycopy(constructorType.ptypes(), 0, initPtypes, 1,
                               constructorType.ptypes().length);
  
              // Set the return type for the <init> MethodType to be void.
              return MethodType.methodType(void.class, initPtypes);
          }
  
          /**
           * Produces an early-bound method handle for a virtual method.
           * It will bypass checks for overriding methods on the receiver,
           * <a href="MethodHandles.Lookup.html#equiv">as if called</a> from an {@code invokespecial}
           * instruction from within the explicitly specified {@code specialCaller}.
           * The type of the method handle will be that of the method,
           * with a suitably restricted receiver type prepended.
           * (The receiver type will be {@code specialCaller} or a subtype.)
           * The method and all its argument types must be accessible
           * to the lookup object.
           * <p>
           * Before method resolution,
           * if the explicitly specified caller class is not identical with the
           * lookup class, or if this lookup object does not have
           * <a href="MethodHandles.Lookup.html#privacc">private access</a>
           * privileges, the access fails.
           * <p>
           * The returned method handle will have
           * {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
           * the method's variable arity modifier bit ({@code 0x0080}) is set.
           * <p style="font-size:smaller;">
           * <em>(Note:  JVM internal methods named {@code "<init>"} are not visible to this API,
           * even though the {@code invokespecial} instruction can refer to them
           * in special circumstances.  Use {@link #findConstructor findConstructor}
           * to access instance initialization methods in a safe manner.)</em>
           * <p><b>Example:</b>
           * <blockquote><pre>{@code
  import static java.lang.invoke.MethodHandles.*;
  import static java.lang.invoke.MethodType.*;
  ...
  static class Listie extends ArrayList {
    public String toString() { return "[wee Listie]"; }
    static Lookup lookup() { return MethodHandles.lookup(); }
  }
  ...
  // no access to constructor via invokeSpecial:
  MethodHandle MH_newListie = Listie.lookup()
    .findConstructor(Listie.class, methodType(void.class));
  Listie l = (Listie) MH_newListie.invokeExact();
  try { assertEquals("impossible", Listie.lookup().findSpecial(
          Listie.class, "<init>", methodType(void.class), Listie.class));
   } catch (NoSuchMethodException ex) { } // OK
  // access to super and self methods via invokeSpecial:
  MethodHandle MH_super = Listie.lookup().findSpecial(
    ArrayList.class, "toString" , methodType(String.class), Listie.class);
  MethodHandle MH_this = Listie.lookup().findSpecial(
    Listie.class, "toString" , methodType(String.class), Listie.class);
  MethodHandle MH_duper = Listie.lookup().findSpecial(
    Object.class, "toString" , methodType(String.class), Listie.class);
  assertEquals("[]", (String) MH_super.invokeExact(l));
  assertEquals(""+l, (String) MH_this.invokeExact(l));
  assertEquals("[]", (String) MH_duper.invokeExact(l)); // ArrayList method
  try { assertEquals("inaccessible", Listie.lookup().findSpecial(
          String.class, "toString", methodType(String.class), Listie.class));
   } catch (IllegalAccessException ex) { } // OK
  Listie subl = new Listie() { public String toString() { return "[subclass]"; } };
  assertEquals(""+l, (String) MH_this.invokeExact(subl)); // Listie method
           * }</pre></blockquote>
           *
           * @param refc the class or interface from which the method is accessed
           * @param name the name of the method (which must not be "&lt;init&gt;")
           * @param type the type of the method, with the receiver argument omitted
           * @param specialCaller the proposed calling class to perform the {@code invokespecial}
           * @return the desired method handle
           * @throws NoSuchMethodException if the method does not exist
           * @throws IllegalAccessException if access checking fails
           *                                or if the method's variable arity modifier bit
           *                                is set and {@code asVarargsCollector} fails
           * @exception SecurityException if a security manager is present and it
           *                              <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
           * @throws NullPointerException if any argument is null
           */
          public MethodHandle findSpecial(Class<?> refc, String name, MethodType type,
                                          Class<?> specialCaller) throws NoSuchMethodException, IllegalAccessException {
              if (specialCaller == null) {
                  throw new NullPointerException("specialCaller == null");
              }
  
              if (type == null) {
                  throw new NullPointerException("type == null");
              }
  
              if (name == null) {
                  throw new NullPointerException("name == null");
              }
  
              if (refc == null) {
                  throw new NullPointerException("ref == null");
              }
  
              // Make sure that the special caller is identical to the lookup class or that we have
              // private access.
              // Android-changed: Also allow access to any interface methods.
              checkSpecialCaller(specialCaller, refc);
  
              // Even though constructors are invoked using a "special" invoke, handles to them can't
              // be created using findSpecial. Callers must use findConstructor instead. Similarly,
              // there is no path for calling static class initializers.
              if (name.startsWith("<")) {
                  throw new NoSuchMethodException(name + " is not a valid method name.");
              }
  
              Method method = refc.getDeclaredMethod(name, type.ptypes());
              checkReturnType(method, type);
              return findSpecial(method, type, refc, specialCaller);
          }
  
          private MethodHandle findSpecial(Method method, MethodType type,
                                           Class<?> refc, Class<?> specialCaller)
                  throws IllegalAccessException {
              if (Modifier.isStatic(method.getModifiers())) {
                  throw new IllegalAccessException("expected a non-static method:" + method);
              }
  
              if (Modifier.isPrivate(method.getModifiers())) {
                  // Since this is a private method, we'll need to also make sure that the
                  // lookup class is the same as the refering class. We've already checked that
                  // the specialCaller is the same as the special lookup class, both of these must
                  // be the same as the declaring class(*) in order to access the private method.
                  //
                  // (*) Well, this isn't true for nested classes but OpenJDK doesn't support those
                  // either.
                  if (refc != lookupClass()) {
                      throw new IllegalAccessException("no private access for invokespecial : "
                              + refc + ", from" + this);
                  }
  
                  // This is a private method, so there's nothing special to do.
                  MethodType handleType = type.insertParameterTypes(0, refc);
                  return createMethodHandle(method, MethodHandle.INVOKE_DIRECT, handleType);
              }
  
              // This is a public, protected or package-private method, which means we're expecting
              // invoke-super semantics. We'll have to restrict the receiver type appropriately on the
              // handle once we check that there really is a "super" relationship between them.
              if (!method.getDeclaringClass().isAssignableFrom(specialCaller)) {
                  throw new IllegalAccessException(refc + "is not assignable from " + specialCaller);
              }
  
              // Note that we restrict the receiver to "specialCaller" instances.
              MethodType handleType = type.insertParameterTypes(0, specialCaller);
              return createMethodHandle(method, MethodHandle.INVOKE_SUPER, handleType);
          }
  
          /**
           * Produces a method handle giving read access to a non-static field.
           * The type of the method handle will have a return type of the field's
           * value type.
           * The method handle's single argument will be the instance containing
           * the field.
           * Access checking is performed immediately on behalf of the lookup class.
           * @param refc the class or interface from which the method is accessed
           * @param name the field's name
           * @param type the field's type
           * @return a method handle which can load values from the field
           * @throws NoSuchFieldException if the field does not exist
           * @throws IllegalAccessException if access checking fails, or if the field is {@code static}
           * @exception SecurityException if a security manager is present and it
           *                              <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
           * @throws NullPointerException if any argument is null
           */
          public MethodHandle findGetter(Class<?> refc, String name, Class<?> type) throws NoSuchFieldException, IllegalAccessException {
              return findAccessor(refc, name, type, MethodHandle.IGET);
          }
  
          private MethodHandle findAccessor(Class<?> refc, String name, Class<?> type, int kind)
              throws NoSuchFieldException, IllegalAccessException {
              final Field field = findFieldOfType(refc, name, type);
              return findAccessor(field, refc, type, kind, true /* performAccessChecks */);
          }
  
          private MethodHandle findAccessor(Field field, Class<?> refc, Class<?> type, int kind,
                                            boolean performAccessChecks)
                  throws IllegalAccessException {
              final boolean isSetterKind = kind == MethodHandle.IPUT || kind == MethodHandle.SPUT;
              final boolean isStaticKind = kind == MethodHandle.SGET || kind == MethodHandle.SPUT;
              commonFieldChecks(field, refc, type, isStaticKind, performAccessChecks);
              if (performAccessChecks) {
                  final int modifiers = field.getModifiers();
                  if (isSetterKind && Modifier.isFinal(modifiers)) {
                      throw new IllegalAccessException("Field " + field + " is final");
                  }
              }
  
              final MethodType methodType;
              switch (kind) {
                  case MethodHandle.SGET:
                      methodType = MethodType.methodType(type);
                      break;
                  case MethodHandle.SPUT:
                      methodType = MethodType.methodType(void.class, type);
                      break;
                  case MethodHandle.IGET:
                      methodType = MethodType.methodType(type, refc);
                      break;
                  case MethodHandle.IPUT:
                      methodType = MethodType.methodType(void.class, refc, type);
                      break;
                  default:
                      throw new IllegalArgumentException("Invalid kind " + kind);
              }
              return new MethodHandleImpl(field.getArtField(), kind, methodType);
          }
  
          /**
           * Produces a method handle giving write access to a non-static field.
           * The type of the method handle will have a void return type.
           * The method handle will take two arguments, the instance containing
           * the field, and the value to be stored.
           * The second argument will be of the field's value type.
           * Access checking is performed immediately on behalf of the lookup class.
           * @param refc the class or interface from which the method is accessed
           * @param name the field's name
           * @param type the field's type
           * @return a method handle which can store values into the field
           * @throws NoSuchFieldException if the field does not exist
           * @throws IllegalAccessException if access checking fails, or if the field is {@code static}
           * @exception SecurityException if a security manager is present and it
           *                              <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
           * @throws NullPointerException if any argument is null
           */
          public MethodHandle findSetter(Class<?> refc, String name, Class<?> type) throws NoSuchFieldException, IllegalAccessException {
              return findAccessor(refc, name, type, MethodHandle.IPUT);
          }
  
          // BEGIN Android-changed: OpenJDK 9+181 VarHandle API factory method.
          /**
           * Produces a VarHandle giving access to a non-static field {@code name}
           * of type {@code type} declared in a class of type {@code recv}.
           * The VarHandle's variable type is {@code type} and it has one
           * coordinate type, {@code recv}.
           * <p>
           * Access checking is performed immediately on behalf of the lookup
           * class.
           * <p>
           * Certain access modes of the returned VarHandle are unsupported under
           * the following conditions:
           * <ul>
           * <li>if the field is declared {@code final}, then the write, atomic
           *     update, numeric atomic update, and bitwise atomic update access
           *     modes are unsupported.
           * <li>if the field type is anything other than {@code byte},
           *     {@code short}, {@code char}, {@code int}, {@code long},
           *     {@code float}, or {@code double} then numeric atomic update
           *     access modes are unsupported.
           * <li>if the field type is anything other than {@code boolean},
           *     {@code byte}, {@code short}, {@code char}, {@code int} or
           *     {@code long} then bitwise atomic update access modes are
           *     unsupported.
           * </ul>
           * <p>
           * If the field is declared {@code volatile} then the returned VarHandle
           * will override access to the field (effectively ignore the
           * {@code volatile} declaration) in accordance to its specified
           * access modes.
           * <p>
           * If the field type is {@code float} or {@code double} then numeric
           * and atomic update access modes compare values using their bitwise
           * representation (see {@link Float#floatToRawIntBits} and
           * {@link Double#doubleToRawLongBits}, respectively).
           * @apiNote
           * Bitwise comparison of {@code float} values or {@code double} values,
           * as performed by the numeric and atomic update access modes, differ
           * from the primitive {@code ==} operator and the {@link Float#equals}
           * and {@link Double#equals} methods, specifically with respect to
           * comparing NaN values or comparing {@code -0.0} with {@code +0.0}.
           * Care should be taken when performing a compare and set or a compare
           * and exchange operation with such values since the operation may
           * unexpectedly fail.
           * There are many possible NaN values that are considered to be
           * {@code NaN} in Java, although no IEEE 754 floating-point operation
           * provided by Java can distinguish between them.  Operation failure can
           * occur if the expected or witness value is a NaN value and it is
           * transformed (perhaps in a platform specific manner) into another NaN
           * value, and thus has a different bitwise representation (see
           * {@link Float#intBitsToFloat} or {@link Double#longBitsToDouble} for more
           * details).
           * The values {@code -0.0} and {@code +0.0} have different bitwise
           * representations but are considered equal when using the primitive
           * {@code ==} operator.  Operation failure can occur if, for example, a
           * numeric algorithm computes an expected value to be say {@code -0.0}
           * and previously computed the witness value to be say {@code +0.0}.
           * @param recv the receiver class, of type {@code R}, that declares the
           * non-static field
           * @param name the field's name
           * @param type the field's type, of type {@code T}
           * @return a VarHandle giving access to non-static fields.
           * @throws NoSuchFieldException if the field does not exist
           * @throws IllegalAccessException if access checking fails, or if the field is {@code static}
           * @exception SecurityException if a security manager is present and it
           *                              <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
           * @throws NullPointerException if any argument is null
           * @since 9
           * @hide
           */
          public VarHandle findVarHandle(Class<?> recv, String name, Class<?> type) throws NoSuchFieldException, IllegalAccessException {
              final Field field = findFieldOfType(recv, name, type);
              final boolean isStatic = false;
              final boolean performAccessChecks = true;
              commonFieldChecks(field, recv, type, isStatic, performAccessChecks);
              return FieldVarHandle.create(field);
          }
          // END Android-changed: OpenJDK 9+181 VarHandle API factory method.
  
          // BEGIN Android-added: Common field resolution and access check methods.
          private Field findFieldOfType(final Class<?> refc, String name, Class<?> type)
                  throws NoSuchFieldException {
              Field field = null;
  
              // Search refc and super classes for the field.
              for (Class<?> cls = refc; cls != null; cls = cls.getSuperclass()) {
                  try {
                      field = cls.getDeclaredField(name);
                      break;
                  } catch (NoSuchFieldException e) {
                  }
              }
  
              if (field == null) {
                  // Force failure citing refc.
                  field = refc.getDeclaredField(name);
              }
  
              final Class<?> fieldType = field.getType();
              if (fieldType != type) {
                  throw new NoSuchFieldException(name);
              }
              return field;
          }
  
          private void commonFieldChecks(Field field, Class<?> refc, Class<?> type,
                                         boolean isStatic, boolean performAccessChecks)
                  throws IllegalAccessException {
              final int modifiers = field.getModifiers();
              if (performAccessChecks) {
                  checkAccess(refc, field.getDeclaringClass(), modifiers, field.getName());
              }
              if (Modifier.isStatic(modifiers) != isStatic) {
                  String reason = "Field " + field + " is " +
                          (isStatic ? "not " : "") + "static";
                  throw new IllegalAccessException(reason);
              }
          }
          // END Android-added: Common field resolution and access check methods.
  
          /**
           * Produces a method handle giving read access to a static field.
           * The type of the method handle will have a return type of the field's
           * value type.
           * The method handle will take no arguments.
           * Access checking is performed immediately on behalf of the lookup class.
           * <p>
           * If the returned method handle is invoked, the field's class will
           * be initialized, if it has not already been initialized.
           * @param refc the class or interface from which the method is accessed
           * @param name the field's name
           * @param type the field's type
           * @return a method handle which can load values from the field
           * @throws NoSuchFieldException if the field does not exist
           * @throws IllegalAccessException if access checking fails, or if the field is not {@code static}
           * @exception SecurityException if a security manager is present and it
           *                              <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
           * @throws NullPointerException if any argument is null
           */
          public MethodHandle findStaticGetter(Class<?> refc, String name, Class<?> type) throws NoSuchFieldException, IllegalAccessException {
              return findAccessor(refc, name, type, MethodHandle.SGET);
          }
  
          /**
           * Produces a method handle giving write access to a static field.
           * The type of the method handle will have a void return type.
           * The method handle will take a single
           * argument, of the field's value type, the value to be stored.
           * Access checking is performed immediately on behalf of the lookup class.
           * <p>
           * If the returned method handle is invoked, the field's class will
           * be initialized, if it has not already been initialized.
           * @param refc the class or interface from which the method is accessed
           * @param name the field's name
           * @param type the field's type
           * @return a method handle which can store values into the field
           * @throws NoSuchFieldException if the field does not exist
           * @throws IllegalAccessException if access checking fails, or if the field is not {@code static}
           * @exception SecurityException if a security manager is present and it
           *                              <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
           * @throws NullPointerException if any argument is null
           */
          public MethodHandle findStaticSetter(Class<?> refc, String name, Class<?> type) throws NoSuchFieldException, IllegalAccessException {
              return findAccessor(refc, name, type, MethodHandle.SPUT);
          }
  
          // BEGIN Android-changed: OpenJDK 9+181 VarHandle API factory method.
          /**
           * Produces a VarHandle giving access to a static field {@code name} of
           * type {@code type} declared in a class of type {@code decl}.
           * The VarHandle's variable type is {@code type} and it has no
           * coordinate types.
           * <p>
           * Access checking is performed immediately on behalf of the lookup
           * class.
           * <p>
           * If the returned VarHandle is operated on, the declaring class will be
           * initialized, if it has not already been initialized.
           * <p>
           * Certain access modes of the returned VarHandle are unsupported under
           * the following conditions:
           * <ul>
           * <li>if the field is declared {@code final}, then the write, atomic
           *     update, numeric atomic update, and bitwise atomic update access
           *     modes are unsupported.
           * <li>if the field type is anything other than {@code byte},
           *     {@code short}, {@code char}, {@code int}, {@code long},
           *     {@code float}, or {@code double}, then numeric atomic update
           *     access modes are unsupported.
           * <li>if the field type is anything other than {@code boolean},
           *     {@code byte}, {@code short}, {@code char}, {@code int} or
           *     {@code long} then bitwise atomic update access modes are
           *     unsupported.
           * </ul>
           * <p>
           * If the field is declared {@code volatile} then the returned VarHandle
           * will override access to the field (effectively ignore the
           * {@code volatile} declaration) in accordance to its specified
           * access modes.
           * <p>
           * If the field type is {@code float} or {@code double} then numeric
           * and atomic update access modes compare values using their bitwise
           * representation (see {@link Float#floatToRawIntBits} and
           * {@link Double#doubleToRawLongBits}, respectively).
           * @apiNote
           * Bitwise comparison of {@code float} values or {@code double} values,
           * as performed by the numeric and atomic update access modes, differ
           * from the primitive {@code ==} operator and the {@link Float#equals}
           * and {@link Double#equals} methods, specifically with respect to
           * comparing NaN values or comparing {@code -0.0} with {@code +0.0}.
           * Care should be taken when performing a compare and set or a compare
           * and exchange operation with such values since the operation may
           * unexpectedly fail.
           * There are many possible NaN values that are considered to be
           * {@code NaN} in Java, although no IEEE 754 floating-point operation
           * provided by Java can distinguish between them.  Operation failure can
           * occur if the expected or witness value is a NaN value and it is
           * transformed (perhaps in a platform specific manner) into another NaN
           * value, and thus has a different bitwise representation (see
           * {@link Float#intBitsToFloat} or {@link Double#longBitsToDouble} for more
           * details).
           * The values {@code -0.0} and {@code +0.0} have different bitwise
           * representations but are considered equal when using the primitive
           * {@code ==} operator.  Operation failure can occur if, for example, a
           * numeric algorithm computes an expected value to be say {@code -0.0}
           * and previously computed the witness value to be say {@code +0.0}.
           * @param decl the class that declares the static field
           * @param name the field's name
           * @param type the field's type, of type {@code T}
           * @return a VarHandle giving access to a static field
           * @throws NoSuchFieldException if the field does not exist
           * @throws IllegalAccessException if access checking fails, or if the field is not {@code static}
           * @exception SecurityException if a security manager is present and it
           *                              <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
           * @throws NullPointerException if any argument is null
           * @since 9
           * @hide
           */
          public VarHandle findStaticVarHandle(Class<?> decl, String name, Class<?> type) throws NoSuchFieldException, IllegalAccessException {
              final Field field = findFieldOfType(decl, name, type);
              final boolean isStatic = true;
              final boolean performAccessChecks = true;
              commonFieldChecks(field, decl, type, isStatic, performAccessChecks);
              return FieldVarHandle.create(field);
          }
          // END Android-changed: OpenJDK 9+181 VarHandle API factory method.
  
          /**
           * Produces an early-bound method handle for a non-static method.
           * The receiver must have a supertype {@code defc} in which a method
           * of the given name and type is accessible to the lookup class.
           * The method and all its argument types must be accessible to the lookup object.
           * The type of the method handle will be that of the method,
           * without any insertion of an additional receiver parameter.
           * The given receiver will be bound into the method handle,
           * so that every call to the method handle will invoke the
           * requested method on the given receiver.
           * <p>
           * The returned method handle will have
           * {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
           * the method's variable arity modifier bit ({@code 0x0080}) is set
           * <em>and</em> the trailing array argument is not the only argument.
           * (If the trailing array argument is the only argument,
           * the given receiver value will be bound to it.)
           * <p>
           * This is equivalent to the following code:
           * <blockquote><pre>{@code
  import static java.lang.invoke.MethodHandles.*;
  import static java.lang.invoke.MethodType.*;
  ...
  MethodHandle mh0 = lookup().findVirtual(defc, name, type);
  MethodHandle mh1 = mh0.bindTo(receiver);
  MethodType mt1 = mh1.type();
  if (mh0.isVarargsCollector())
    mh1 = mh1.asVarargsCollector(mt1.parameterType(mt1.parameterCount()-1));
  return mh1;
           * }</pre></blockquote>
           * where {@code defc} is either {@code receiver.getClass()} or a super
           * type of that class, in which the requested method is accessible
           * to the lookup class.
           * (Note that {@code bindTo} does not preserve variable arity.)
           * @param receiver the object from which the method is accessed
           * @param name the name of the method
           * @param type the type of the method, with the receiver argument omitted
           * @return the desired method handle
           * @throws NoSuchMethodException if the method does not exist
           * @throws IllegalAccessException if access checking fails
           *                                or if the method's variable arity modifier bit
           *                                is set and {@code asVarargsCollector} fails
           * @exception SecurityException if a security manager is present and it
           *                              <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
           * @throws NullPointerException if any argument is null
           * @see MethodHandle#bindTo
           * @see #findVirtual
           */
          public MethodHandle bind(Object receiver, String name, MethodType type) throws NoSuchMethodException, IllegalAccessException {
              MethodHandle handle = findVirtual(receiver.getClass(), name, type);
              MethodHandle adapter = handle.bindTo(receiver);
              MethodType adapterType = adapter.type();
              if (handle.isVarargsCollector()) {
                  adapter = adapter.asVarargsCollector(
                          adapterType.parameterType(adapterType.parameterCount() - 1));
              }
  
              return adapter;
          }
  
          /**
           * Makes a <a href="MethodHandleInfo.html#directmh">direct method handle</a>
           * to <i>m</i>, if the lookup class has permission.
           * If <i>m</i> is non-static, the receiver argument is treated as an initial argument.
           * If <i>m</i> is virtual, overriding is respected on every call.
           * Unlike the Core Reflection API, exceptions are <em>not</em> wrapped.
           * The type of the method handle will be that of the method,
           * with the receiver type prepended (but only if it is non-static).
           * If the method's {@code accessible} flag is not set,
           * access checking is performed immediately on behalf of the lookup class.
           * If <i>m</i> is not public, do not share the resulting handle with untrusted parties.
           * <p>
           * The returned method handle will have
           * {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
           * the method's variable arity modifier bit ({@code 0x0080}) is set.
           * <p>
           * If <i>m</i> is static, and
           * if the returned method handle is invoked, the method's class will
           * be initialized, if it has not already been initialized.
           * @param m the reflected method
           * @return a method handle which can invoke the reflected method
           * @throws IllegalAccessException if access checking fails
           *                                or if the method's variable arity modifier bit
           *                                is set and {@code asVarargsCollector} fails
           * @throws NullPointerException if the argument is null
           */
          public MethodHandle unreflect(Method m) throws IllegalAccessException {
              if (m == null) {
                  throw new NullPointerException("m == null");
              }
  
              MethodType methodType = MethodType.methodType(m.getReturnType(),
                      m.getParameterTypes());
  
              // We should only perform access checks if setAccessible hasn't been called yet.
              if (!m.isAccessible()) {
                  checkAccess(m.getDeclaringClass(), m.getDeclaringClass(), m.getModifiers(),
                          m.getName());
              }
  
              if (Modifier.isStatic(m.getModifiers())) {
                  return createMethodHandle(m, MethodHandle.INVOKE_STATIC, methodType);
              } else {
                  methodType = methodType.insertParameterTypes(0, m.getDeclaringClass());
                  return createMethodHandle(m, MethodHandle.INVOKE_VIRTUAL, methodType);
              }
          }
  
          /**
           * Produces a method handle for a reflected method.
           * It will bypass checks for overriding methods on the receiver,
           * <a href="MethodHandles.Lookup.html#equiv">as if called</a> from an {@code invokespecial}
           * instruction from within the explicitly specified {@code specialCaller}.
           * The type of the method handle will be that of the method,
           * with a suitably restricted receiver type prepended.
           * (The receiver type will be {@code specialCaller} or a subtype.)
           * If the method's {@code accessible} flag is not set,
           * access checking is performed immediately on behalf of the lookup class,
           * as if {@code invokespecial} instruction were being linked.
           * <p>
           * Before method resolution,
           * if the explicitly specified caller class is not identical with the
           * lookup class, or if this lookup object does not have
           * <a href="MethodHandles.Lookup.html#privacc">private access</a>
           * privileges, the access fails.
           * <p>
           * The returned method handle will have
           * {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
           * the method's variable arity modifier bit ({@code 0x0080}) is set.
           * @param m the reflected method
           * @param specialCaller the class nominally calling the method
           * @return a method handle which can invoke the reflected method
           * @throws IllegalAccessException if access checking fails
           *                                or if the method's variable arity modifier bit
           *                                is set and {@code asVarargsCollector} fails
           * @throws NullPointerException if any argument is null
           */
          public MethodHandle unreflectSpecial(Method m, Class<?> specialCaller) throws IllegalAccessException {
              if (m == null) {
                  throw new NullPointerException("m == null");
              }
  
              if (specialCaller == null) {
                  throw new NullPointerException("specialCaller == null");
              }
  
              if (!m.isAccessible()) {
                  // Android-changed: Match Java language 9 behavior where unreflectSpecial continues
                  // to require exact caller lookupClass match.
                  checkSpecialCaller(specialCaller, null);
              }
  
              final MethodType methodType = MethodType.methodType(m.getReturnType(),
                      m.getParameterTypes());
              return findSpecial(m, methodType, m.getDeclaringClass() /* refc */, specialCaller);
          }
  
          /**
           * Produces a method handle for a reflected constructor.
           * The type of the method handle will be that of the constructor,
           * with the return type changed to the declaring class.
           * The method handle will perform a {@code newInstance} operation,
           * creating a new instance of the constructor's class on the
           * arguments passed to the method handle.
           * <p>
           * If the constructor's {@code accessible} flag is not set,
           * access checking is performed immediately on behalf of the lookup class.
           * <p>
           * The returned method handle will have
           * {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
           * the constructor's variable arity modifier bit ({@code 0x0080}) is set.
           * <p>
           * If the returned method handle is invoked, the constructor's class will
           * be initialized, if it has not already been initialized.
           * @param c the reflected constructor
           * @return a method handle which can invoke the reflected constructor
           * @throws IllegalAccessException if access checking fails
           *                                or if the method's variable arity modifier bit
           *                                is set and {@code asVarargsCollector} fails
           * @throws NullPointerException if the argument is null
           */
          public MethodHandle unreflectConstructor(Constructor<?> c) throws IllegalAccessException {
              if (c == null) {
                  throw new NullPointerException("c == null");
              }
  
              if (!c.isAccessible()) {
                  checkAccess(c.getDeclaringClass(), c.getDeclaringClass(), c.getModifiers(),
                          c.getName());
              }
  
              return createMethodHandleForConstructor(c);
          }
  
          /**
           * Produces a method handle giving read access to a reflected field.
           * The type of the method handle will have a return type of the field's
           * value type.
           * If the field is static, the method handle will take no arguments.
           * Otherwise, its single argument will be the instance containing
           * the field.
           * If the field's {@code accessible} flag is not set,
           * access checking is performed immediately on behalf of the lookup class.
           * <p>
           * If the field is static, and
           * if the returned method handle is invoked, the field's class will
           * be initialized, if it has not already been initialized.
           * @param f the reflected field
           * @return a method handle which can load values from the reflected field
           * @throws IllegalAccessException if access checking fails
           * @throws NullPointerException if the argument is null
           */
          public MethodHandle unreflectGetter(Field f) throws IllegalAccessException {
              return findAccessor(f, f.getDeclaringClass(), f.getType(),
                      Modifier.isStatic(f.getModifiers()) ? MethodHandle.SGET : MethodHandle.IGET,
                      !f.isAccessible() /* performAccessChecks */);
          }
  
          /**
           * Produces a method handle giving write access to a reflected field.
           * The type of the method handle will have a void return type.
           * If the field is static, the method handle will take a single
           * argument, of the field's value type, the value to be stored.
           * Otherwise, the two arguments will be the instance containing
           * the field, and the value to be stored.
           * If the field's {@code accessible} flag is not set,
           * access checking is performed immediately on behalf of the lookup class.
           * <p>
           * If the field is static, and
           * if the returned method handle is invoked, the field's class will
           * be initialized, if it has not already been initialized.
           * @param f the reflected field
           * @return a method handle which can store values into the reflected field
           * @throws IllegalAccessException if access checking fails
           * @throws NullPointerException if the argument is null
           */
          public MethodHandle unreflectSetter(Field f) throws IllegalAccessException {
              return findAccessor(f, f.getDeclaringClass(), f.getType(),
                      Modifier.isStatic(f.getModifiers()) ? MethodHandle.SPUT : MethodHandle.IPUT,
                      !f.isAccessible() /* performAccessChecks */);
          }
  
          // BEGIN Android-changed: OpenJDK 9+181 VarHandle API factory method.
          /**
           * Produces a VarHandle giving access to a reflected field {@code f}
           * of type {@code T} declared in a class of type {@code R}.
           * The VarHandle's variable type is {@code T}.
           * If the field is non-static the VarHandle has one coordinate type,
           * {@code R}.  Otherwise, the field is static, and the VarHandle has no
           * coordinate types.
           * <p>
           * Access checking is performed immediately on behalf of the lookup
           * class, regardless of the value of the field's {@code accessible}
           * flag.
           * <p>
           * If the field is static, and if the returned VarHandle is operated
           * on, the field's declaring class will be initialized, if it has not
           * already been initialized.
           * <p>
           * Certain access modes of the returned VarHandle are unsupported under
           * the following conditions:
           * <ul>
           * <li>if the field is declared {@code final}, then the write, atomic
           *     update, numeric atomic update, and bitwise atomic update access
           *     modes are unsupported.
           * <li>if the field type is anything other than {@code byte},
           *     {@code short}, {@code char}, {@code int}, {@code long},
           *     {@code float}, or {@code double} then numeric atomic update
           *     access modes are unsupported.
           * <li>if the field type is anything other than {@code boolean},
           *     {@code byte}, {@code short}, {@code char}, {@code int} or
           *     {@code long} then bitwise atomic update access modes are
           *     unsupported.
           * </ul>
           * <p>
           * If the field is declared {@code volatile} then the returned VarHandle
           * will override access to the field (effectively ignore the
           * {@code volatile} declaration) in accordance to its specified
           * access modes.
           * <p>
           * If the field type is {@code float} or {@code double} then numeric
           * and atomic update access modes compare values using their bitwise
           * representation (see {@link Float#floatToRawIntBits} and
           * {@link Double#doubleToRawLongBits}, respectively).
           * @apiNote
           * Bitwise comparison of {@code float} values or {@code double} values,
           * as performed by the numeric and atomic update access modes, differ
           * from the primitive {@code ==} operator and the {@link Float#equals}
           * and {@link Double#equals} methods, specifically with respect to
           * comparing NaN values or comparing {@code -0.0} with {@code +0.0}.
           * Care should be taken when performing a compare and set or a compare
           * and exchange operation with such values since the operation may
           * unexpectedly fail.
           * There are many possible NaN values that are considered to be
           * {@code NaN} in Java, although no IEEE 754 floating-point operation
           * provided by Java can distinguish between them.  Operation failure can
           * occur if the expected or witness value is a NaN value and it is
           * transformed (perhaps in a platform specific manner) into another NaN
           * value, and thus has a different bitwise representation (see
           * {@link Float#intBitsToFloat} or {@link Double#longBitsToDouble} for more
           * details).
           * The values {@code -0.0} and {@code +0.0} have different bitwise
           * representations but are considered equal when using the primitive
           * {@code ==} operator.  Operation failure can occur if, for example, a
           * numeric algorithm computes an expected value to be say {@code -0.0}
           * and previously computed the witness value to be say {@code +0.0}.
           * @param f the reflected field, with a field of type {@code T}, and
           * a declaring class of type {@code R}
           * @return a VarHandle giving access to non-static fields or a static
           * field
           * @throws IllegalAccessException if access checking fails
           * @throws NullPointerException if the argument is null
           * @since 9
           * @hide
           */
          public VarHandle unreflectVarHandle(Field f) throws IllegalAccessException {
              final boolean isStatic = Modifier.isStatic(f.getModifiers());
              final boolean performAccessChecks = true;
              commonFieldChecks(f, f.getDeclaringClass(), f.getType(), isStatic, performAccessChecks);
              return FieldVarHandle.create(f);
          }
          // END Android-changed: OpenJDK 9+181 VarHandle API factory method.
  
          /**
           * Cracks a <a href="MethodHandleInfo.html#directmh">direct method handle</a>
           * created by this lookup object or a similar one.
           * Security and access checks are performed to ensure that this lookup object
           * is capable of reproducing the target method handle.
           * This means that the cracking may fail if target is a direct method handle
           * but was created by an unrelated lookup object.
           * This can happen if the method handle is <a href="MethodHandles.Lookup.html#callsens">caller sensitive</a>
           * and was created by a lookup object for a different class.
           * @param target a direct method handle to crack into symbolic reference components
           * @return a symbolic reference which can be used to reconstruct this method handle from this lookup object
           * @exception SecurityException if a security manager is present and it
           *                              <a href="MethodHandles.Lookup.html#secmgr">refuses access</a>
           * @throws IllegalArgumentException if the target is not a direct method handle or if access checking fails
           * @exception NullPointerException if the target is {@code null}
           * @see MethodHandleInfo
           * @since 1.8
           */
          public MethodHandleInfo revealDirect(MethodHandle target) {
              MethodHandleImpl directTarget = getMethodHandleImpl(target);
              MethodHandleInfo info = directTarget.reveal();
  
              try {
                  checkAccess(lookupClass(), info.getDeclaringClass(), info.getModifiers(),
                          info.getName());
              } catch (IllegalAccessException exception) {
                  throw new IllegalArgumentException("Unable to access memeber.", exception);
              }
  
              return info;
          }
  
          private boolean hasPrivateAccess() {
              return (allowedModes & PRIVATE) != 0;
          }
  
          /** Check public/protected/private bits on the symbolic reference class and its member. */
          void checkAccess(Class<?> refc, Class<?> defc, int mods, String methName)
                  throws IllegalAccessException {
              int allowedModes = this.allowedModes;
  
              if (Modifier.isProtected(mods) &&
                      defc == Object.class &&
                      "clone".equals(methName) &&
                      refc.isArray()) {
                  // The JVM does this hack also.
                  // (See ClassVerifier::verify_invoke_instructions
                  // and LinkResolver::check_method_accessability.)
                  // Because the JVM does not allow separate methods on array types,
                  // there is no separate method for int[].clone.
                  // All arrays simply inherit Object.clone.
                  // But for access checking logic, we make Object.clone
                  // (normally protected) appear to be public.
                  // Later on, when the DirectMethodHandle is created,
                  // its leading argument will be restricted to the
                  // requested array type.
                  // N.B. The return type is not adjusted, because
                  // that is *not* the bytecode behavior.
                  mods ^= Modifier.PROTECTED | Modifier.PUBLIC;
              }
  
              if (Modifier.isProtected(mods) && Modifier.isConstructor(mods)) {
                  // cannot "new" a protected ctor in a different package
                  mods ^= Modifier.PROTECTED;
              }
  
              if (Modifier.isPublic(mods) && Modifier.isPublic(refc.getModifiers()) && allowedModes != 0)
                  return;  // common case
              int requestedModes = fixmods(mods);  // adjust 0 => PACKAGE
              if ((requestedModes & allowedModes) != 0) {
                  if (VerifyAccess.isMemberAccessible(refc, defc, mods, lookupClass(), allowedModes))
                      return;
              } else {
                  // Protected members can also be checked as if they were package-private.
                  if ((requestedModes & PROTECTED) != 0 && (allowedModes & PACKAGE) != 0
                          && VerifyAccess.isSamePackage(defc, lookupClass()))
                      return;
              }
  
              throwMakeAccessException(accessFailedMessage(refc, defc, mods), this);
          }
  
          String accessFailedMessage(Class<?> refc, Class<?> defc, int mods) {
              // check the class first:
              boolean classOK = (Modifier.isPublic(defc.getModifiers()) &&
                      (defc == refc ||
                              Modifier.isPublic(refc.getModifiers())));
              if (!classOK && (allowedModes & PACKAGE) != 0) {
                  classOK = (VerifyAccess.isClassAccessible(defc, lookupClass(), ALL_MODES) &&
                          (defc == refc ||
                                  VerifyAccess.isClassAccessible(refc, lookupClass(), ALL_MODES)));
              }
              if (!classOK)
                  return "class is not public";
              if (Modifier.isPublic(mods))
                  return "access to public member failed";  // (how?)
              if (Modifier.isPrivate(mods))
                  return "member is private";
              if (Modifier.isProtected(mods))
                  return "member is protected";
              return "member is private to package";
          }
  
          // Android-changed: checkSpecialCaller assumes that ALLOW_NESTMATE_ACCESS = false,
          // as in upstream OpenJDK.
          //
          // private static final boolean ALLOW_NESTMATE_ACCESS = false;
  
          // Android-changed: Match java language 9 behavior allowing special access if the reflected
          // class (called 'refc', the class from which the method is being accessed) is an interface
          // and is implemented by the caller.
          private void checkSpecialCaller(Class<?> specialCaller, Class<?> refc) throws IllegalAccessException {
              // Android-changed: No support for TRUSTED lookups. Also construct the
              // IllegalAccessException by hand because the upstream code implicitly assumes
              // that the lookupClass == specialCaller.
              //
              // if (allowedModes == TRUSTED)  return;
              boolean isInterfaceLookup = (refc != null &&
                                           refc.isInterface() &&
                                           refc.isAssignableFrom(specialCaller));
              if (!hasPrivateAccess() || (specialCaller != lookupClass() && !isInterfaceLookup)) {
                  throw new IllegalAccessException("no private access for invokespecial : "
                          + specialCaller + ", from" + this);
              }
          }
  
          private void throwMakeAccessException(String message, Object from) throws
                  IllegalAccessException{
              message = message + ": "+ toString();
              if (from != null)  message += ", from " + from;
              throw new IllegalAccessException(message);
          }
  
          private void checkReturnType(Method method, MethodType methodType)
                  throws NoSuchMethodException {
              if (method.getReturnType() != methodType.rtype()) {
                  throw new NoSuchMethodException(method.getName() + methodType);
              }
          }
      }
  
      /**
       * "Cracks" {@code target} to reveal the underlying {@code MethodHandleImpl}.
       */
      private static MethodHandleImpl getMethodHandleImpl(MethodHandle target) {
          // Special case : We implement handles to constructors as transformers,
          // so we must extract the underlying handle from the transformer.
          if (target instanceof Transformers.Construct) {
              target = ((Transformers.Construct) target).getConstructorHandle();
          }
  
          // Special case: Var-args methods are also implemented as Transformers,
          // so we should get the underlying handle in that case as well.
          if (target instanceof Transformers.VarargsCollector) {
              target = target.asFixedArity();
          }
  
          if (target instanceof MethodHandleImpl) {
              return (MethodHandleImpl) target;
          }
  
          throw new IllegalArgumentException(target + " is not a direct handle");
      }
  
      // BEGIN Android-added: method to check if a class is an array.
      private static void checkClassIsArray(Class<?> c) {
          if (!c.isArray()) {
              throw new IllegalArgumentException("Not an array type: " + c);
          }
      }
  
      private static void checkTypeIsViewable(Class<?> componentType) {
          if (componentType == short.class ||
              componentType == char.class ||
              componentType == int.class ||
              componentType == long.class ||
              componentType == float.class ||
              componentType == double.class) {
              return;
          }
          throw new UnsupportedOperationException("Component type not supported: " + componentType);
      }
      // END Android-added: method to check if a class is an array.
  
      /**
       * Produces a method handle giving read access to elements of an array.
       * The type of the method handle will have a return type of the array's
       * element type.  Its first argument will be the array type,
       * and the second will be {@code int}.
       * @param arrayClass an array type
       * @return a method handle which can load values from the given array type
       * @throws NullPointerException if the argument is null
       * @throws  IllegalArgumentException if arrayClass is not an array type
       */
      public static
      MethodHandle arrayElementGetter(Class<?> arrayClass) throws IllegalArgumentException {
          checkClassIsArray(arrayClass);
          final Class<?> componentType = arrayClass.getComponentType();
          if (componentType.isPrimitive()) {
              try {
                  return Lookup.PUBLIC_LOOKUP.findStatic(MethodHandles.class,
                          "arrayElementGetter",
                          MethodType.methodType(componentType, arrayClass, int.class));
              } catch (NoSuchMethodException | IllegalAccessException exception) {
                  throw new AssertionError(exception);
              }
          }
  
          return new Transformers.ReferenceArrayElementGetter(arrayClass);
      }
  
      /** @hide */ public static byte arrayElementGetter(byte[] array, int i) { return array[i]; }
      /** @hide */ public static boolean arrayElementGetter(boolean[] array, int i) { return array[i]; }
      /** @hide */ public static char arrayElementGetter(char[] array, int i) { return array[i]; }
      /** @hide */ public static short arrayElementGetter(short[] array, int i) { return array[i]; }
      /** @hide */ public static int arrayElementGetter(int[] array, int i) { return array[i]; }
      /** @hide */ public static long arrayElementGetter(long[] array, int i) { return array[i]; }
      /** @hide */ public static float arrayElementGetter(float[] array, int i) { return array[i]; }
      /** @hide */ public static double arrayElementGetter(double[] array, int i) { return array[i]; }
  
      /**
       * Produces a method handle giving write access to elements of an array.
       * The type of the method handle will have a void return type.
       * Its last argument will be the array's element type.
       * The first and second arguments will be the array type and int.
       * @param arrayClass the class of an array
       * @return a method handle which can store values into the array type
       * @throws NullPointerException if the argument is null
       * @throws IllegalArgumentException if arrayClass is not an array type
       */
      public static
      MethodHandle arrayElementSetter(Class<?> arrayClass) throws IllegalArgumentException {
          checkClassIsArray(arrayClass);
          final Class<?> componentType = arrayClass.getComponentType();
          if (componentType.isPrimitive()) {
              try {
                  return Lookup.PUBLIC_LOOKUP.findStatic(MethodHandles.class,
                          "arrayElementSetter",
                          MethodType.methodType(void.class, arrayClass, int.class, componentType));
              } catch (NoSuchMethodException | IllegalAccessException exception) {
                  throw new AssertionError(exception);
              }
          }
  
          return new Transformers.ReferenceArrayElementSetter(arrayClass);
      }
  
      /** @hide */
      public static void arrayElementSetter(byte[] array, int i, byte val) { array[i] = val; }
      /** @hide */
      public static void arrayElementSetter(boolean[] array, int i, boolean val) { array[i] = val; }
      /** @hide */
      public static void arrayElementSetter(char[] array, int i, char val) { array[i] = val; }
      /** @hide */
      public static void arrayElementSetter(short[] array, int i, short val) { array[i] = val; }
      /** @hide */
      public static void arrayElementSetter(int[] array, int i, int val) { array[i] = val; }
      /** @hide */
      public static void arrayElementSetter(long[] array, int i, long val) { array[i] = val; }
      /** @hide */
      public static void arrayElementSetter(float[] array, int i, float val) { array[i] = val; }
      /** @hide */
      public static void arrayElementSetter(double[] array, int i, double val) { array[i] = val; }
  
      // BEGIN Android-changed: OpenJDK 9+181 VarHandle API factory methods.
      /**
       * Produces a VarHandle giving access to elements of an array of type
       * {@code arrayClass}.  The VarHandle's variable type is the component type
       * of {@code arrayClass} and the list of coordinate types is
       * {@code (arrayClass, int)}, where the {@code int} coordinate type
       * corresponds to an argument that is an index into an array.
       * <p>
       * Certain access modes of the returned VarHandle are unsupported under
       * the following conditions:
       * <ul>
       * <li>if the component type is anything other than {@code byte},
       *     {@code short}, {@code char}, {@code int}, {@code long},
       *     {@code float}, or {@code double} then numeric atomic update access
       *     modes are unsupported.
       * <li>if the field type is anything other than {@code boolean},
       *     {@code byte}, {@code short}, {@code char}, {@code int} or
       *     {@code long} then bitwise atomic update access modes are
       *     unsupported.
       * </ul>
       * <p>
       * If the component type is {@code float} or {@code double} then numeric
       * and atomic update access modes compare values using their bitwise
       * representation (see {@link Float#floatToRawIntBits} and
       * {@link Double#doubleToRawLongBits}, respectively).
       * @apiNote
       * Bitwise comparison of {@code float} values or {@code double} values,
       * as performed by the numeric and atomic update access modes, differ
       * from the primitive {@code ==} operator and the {@link Float#equals}
       * and {@link Double#equals} methods, specifically with respect to
       * comparing NaN values or comparing {@code -0.0} with {@code +0.0}.
       * Care should be taken when performing a compare and set or a compare
       * and exchange operation with such values since the operation may
       * unexpectedly fail.
       * There are many possible NaN values that are considered to be
       * {@code NaN} in Java, although no IEEE 754 floating-point operation
       * provided by Java can distinguish between them.  Operation failure can
       * occur if the expected or witness value is a NaN value and it is
       * transformed (perhaps in a platform specific manner) into another NaN
       * value, and thus has a different bitwise representation (see
       * {@link Float#intBitsToFloat} or {@link Double#longBitsToDouble} for more
       * details).
       * The values {@code -0.0} and {@code +0.0} have different bitwise
       * representations but are considered equal when using the primitive
       * {@code ==} operator.  Operation failure can occur if, for example, a
       * numeric algorithm computes an expected value to be say {@code -0.0}
       * and previously computed the witness value to be say {@code +0.0}.
       * @param arrayClass the class of an array, of type {@code T[]}
       * @return a VarHandle giving access to elements of an array
       * @throws NullPointerException if the arrayClass is null
       * @throws IllegalArgumentException if arrayClass is not an array type
       * @since 9
       * @hide
       */
      public static
      VarHandle arrayElementVarHandle(Class<?> arrayClass) throws IllegalArgumentException {
          checkClassIsArray(arrayClass);
          return ArrayElementVarHandle.create(arrayClass);
      }
  
      /**
       * Produces a VarHandle giving access to elements of a {@code byte[]} array
       * viewed as if it were a different primitive array type, such as
       * {@code int[]} or {@code long[]}.
       * The VarHandle's variable type is the component type of
       * {@code viewArrayClass} and the list of coordinate types is
       * {@code (byte[], int)}, where the {@code int} coordinate type
       * corresponds to an argument that is an index into a {@code byte[]} array.
       * The returned VarHandle accesses bytes at an index in a {@code byte[]}
       * array, composing bytes to or from a value of the component type of
       * {@code viewArrayClass} according to the given endianness.
       * <p>
       * The supported component types (variables types) are {@code short},
       * {@code char}, {@code int}, {@code long}, {@code float} and
       * {@code double}.
       * <p>
       * Access of bytes at a given index will result in an
       * {@code IndexOutOfBoundsException} if the index is less than {@code 0}
       * or greater than the {@code byte[]} array length minus the size (in bytes)
       * of {@code T}.
       * <p>
       * Access of bytes at an index may be aligned or misaligned for {@code T},
       * with respect to the underlying memory address, {@code A} say, associated
       * with the array and index.
       * If access is misaligned then access for anything other than the
       * {@code get} and {@code set} access modes will result in an
       * {@code IllegalStateException}.  In such cases atomic access is only
       * guaranteed with respect to the largest power of two that divides the GCD
       * of {@code A} and the size (in bytes) of {@code T}.
       * If access is aligned then following access modes are supported and are
       * guaranteed to support atomic access:
       * <ul>
       * <li>read write access modes for all {@code T}, with the exception of
       *     access modes {@code get} and {@code set} for {@code long} and
       *     {@code double} on 32-bit platforms.
       * <li>atomic update access modes for {@code int}, {@code long},
       *     {@code float} or {@code double}.
       *     (Future major platform releases of the JDK may support additional
       *     types for certain currently unsupported access modes.)
       * <li>numeric atomic update access modes for {@code int} and {@code long}.
       *     (Future major platform releases of the JDK may support additional
       *     numeric types for certain currently unsupported access modes.)
       * <li>bitwise atomic update access modes for {@code int} and {@code long}.
       *     (Future major platform releases of the JDK may support additional
       *     numeric types for certain currently unsupported access modes.)
       * </ul>
       * <p>
       * Misaligned access, and therefore atomicity guarantees, may be determined
       * for {@code byte[]} arrays without operating on a specific array.  Given
       * an {@code index}, {@code T} and it's corresponding boxed type,
       * {@code T_BOX}, misalignment may be determined as follows:
       * <pre>{@code
       * int sizeOfT = T_BOX.BYTES;  // size in bytes of T
       * int misalignedAtZeroIndex = ByteBuffer.wrap(new byte[0]).
       *     alignmentOffset(0, sizeOfT);
       * int misalignedAtIndex = (misalignedAtZeroIndex + index) % sizeOfT;
       * boolean isMisaligned = misalignedAtIndex != 0;
       * }</pre>
       * <p>
       * If the variable type is {@code float} or {@code double} then atomic
       * update access modes compare values using their bitwise representation
       * (see {@link Float#floatToRawIntBits} and
       * {@link Double#doubleToRawLongBits}, respectively).
       * @param viewArrayClass the view array class, with a component type of
       * type {@code T}
       * @param byteOrder the endianness of the view array elements, as
       * stored in the underlying {@code byte} array
       * @return a VarHandle giving access to elements of a {@code byte[]} array
       * viewed as if elements corresponding to the components type of the view
       * array class
       * @throws NullPointerException if viewArrayClass or byteOrder is null
       * @throws IllegalArgumentException if viewArrayClass is not an array type
       * @throws UnsupportedOperationException if the component type of
       * viewArrayClass is not supported as a variable type
       * @since 9
       * @hide
       */
      public static
      VarHandle byteArrayViewVarHandle(Class<?> viewArrayClass,
                                       ByteOrder byteOrder) throws IllegalArgumentException {
          checkClassIsArray(viewArrayClass);
          checkTypeIsViewable(viewArrayClass.getComponentType());
          return ByteArrayViewVarHandle.create(viewArrayClass, byteOrder);
      }
  
      /**
       * Produces a VarHandle giving access to elements of a {@code ByteBuffer}
       * viewed as if it were an array of elements of a different primitive
       * component type to that of {@code byte}, such as {@code int[]} or
       * {@code long[]}.
       * The VarHandle's variable type is the component type of
       * {@code viewArrayClass} and the list of coordinate types is
       * {@code (ByteBuffer, int)}, where the {@code int} coordinate type
       * corresponds to an argument that is an index into a {@code byte[]} array.
       * The returned VarHandle accesses bytes at an index in a
       * {@code ByteBuffer}, composing bytes to or from a value of the component
       * type of {@code viewArrayClass} according to the given endianness.
       * <p>
       * The supported component types (variables types) are {@code short},
       * {@code char}, {@code int}, {@code long}, {@code float} and
       * {@code double}.
       * <p>
       * Access will result in a {@code ReadOnlyBufferException} for anything
       * other than the read access modes if the {@code ByteBuffer} is read-only.
       * <p>
       * Access of bytes at a given index will result in an
       * {@code IndexOutOfBoundsException} if the index is less than {@code 0}
       * or greater than the {@code ByteBuffer} limit minus the size (in bytes) of
       * {@code T}.
       * <p>
       * Access of bytes at an index may be aligned or misaligned for {@code T},
       * with respect to the underlying memory address, {@code A} say, associated
       * with the {@code ByteBuffer} and index.
       * If access is misaligned then access for anything other than the
       * {@code get} and {@code set} access modes will result in an
       * {@code IllegalStateException}.  In such cases atomic access is only
       * guaranteed with respect to the largest power of two that divides the GCD
       * of {@code A} and the size (in bytes) of {@code T}.
       * If access is aligned then following access modes are supported and are
       * guaranteed to support atomic access:
       * <ul>
       * <li>read write access modes for all {@code T}, with the exception of
       *     access modes {@code get} and {@code set} for {@code long} and
       *     {@code double} on 32-bit platforms.
       * <li>atomic update access modes for {@code int}, {@code long},
       *     {@code float} or {@code double}.
       *     (Future major platform releases of the JDK may support additional
       *     types for certain currently unsupported access modes.)
       * <li>numeric atomic update access modes for {@code int} and {@code long}.
       *     (Future major platform releases of the JDK may support additional
       *     numeric types for certain currently unsupported access modes.)
       * <li>bitwise atomic update access modes for {@code int} and {@code long}.
       *     (Future major platform releases of the JDK may support additional
       *     numeric types for certain currently unsupported access modes.)
       * </ul>
       * <p>
       * Misaligned access, and therefore atomicity guarantees, may be determined
       * for a {@code ByteBuffer}, {@code bb} (direct or otherwise), an
       * {@code index}, {@code T} and it's corresponding boxed type,
       * {@code T_BOX}, as follows:
       * <pre>{@code
       * int sizeOfT = T_BOX.BYTES;  // size in bytes of T
       * ByteBuffer bb = ...
       * int misalignedAtIndex = bb.alignmentOffset(index, sizeOfT);
       * boolean isMisaligned = misalignedAtIndex != 0;
       * }</pre>
       * <p>
       * If the variable type is {@code float} or {@code double} then atomic
       * update access modes compare values using their bitwise representation
       * (see {@link Float#floatToRawIntBits} and
       * {@link Double#doubleToRawLongBits}, respectively).
       * @param viewArrayClass the view array class, with a component type of
       * type {@code T}
       * @param byteOrder the endianness of the view array elements, as
       * stored in the underlying {@code ByteBuffer} (Note this overrides the
       * endianness of a {@code ByteBuffer})
       * @return a VarHandle giving access to elements of a {@code ByteBuffer}
       * viewed as if elements corresponding to the components type of the view
       * array class
       * @throws NullPointerException if viewArrayClass or byteOrder is null
       * @throws IllegalArgumentException if viewArrayClass is not an array type
       * @throws UnsupportedOperationException if the component type of
       * viewArrayClass is not supported as a variable type
       * @since 9
       * @hide
       */
      public static
      VarHandle byteBufferViewVarHandle(Class<?> viewArrayClass,
                                        ByteOrder byteOrder) throws IllegalArgumentException {
          checkClassIsArray(viewArrayClass);
          checkTypeIsViewable(viewArrayClass.getComponentType());
          return ByteBufferViewVarHandle.create(viewArrayClass, byteOrder);
      }
      // END Android-changed: OpenJDK 9+181 VarHandle API factory methods.
  
      /// method handle invocation (reflective style)
  
      /**
       * Produces a method handle which will invoke any method handle of the
       * given {@code type}, with a given number of trailing arguments replaced by
       * a single trailing {@code Object[]} array.
       * The resulting invoker will be a method handle with the following
       * arguments:
       * <ul>
       * <li>a single {@code MethodHandle} target
       * <li>zero or more leading values (counted by {@code leadingArgCount})
       * <li>an {@code Object[]} array containing trailing arguments
       * </ul>
       * <p>
       * The invoker will invoke its target like a call to {@link MethodHandle#invoke invoke} with
       * the indicated {@code type}.
       * That is, if the target is exactly of the given {@code type}, it will behave
       * like {@code invokeExact}; otherwise it behave as if {@link MethodHandle#asType asType}
       * is used to convert the target to the required {@code type}.
       * <p>
       * The type of the returned invoker will not be the given {@code type}, but rather
       * will have all parameters except the first {@code leadingArgCount}
       * replaced by a single array of type {@code Object[]}, which will be
       * the final parameter.
       * <p>
       * Before invoking its target, the invoker will spread the final array, apply
       * reference casts as necessary, and unbox and widen primitive arguments.
       * If, when the invoker is called, the supplied array argument does
       * not have the correct number of elements, the invoker will throw
       * an {@link IllegalArgumentException} instead of invoking the target.
       * <p>
       * This method is equivalent to the following code (though it may be more efficient):
       * <blockquote><pre>{@code
  MethodHandle invoker = MethodHandles.invoker(type);
  int spreadArgCount = type.parameterCount() - leadingArgCount;
  invoker = invoker.asSpreader(Object[].class, spreadArgCount);
  return invoker;
       * }</pre></blockquote>
       * This method throws no reflective or security exceptions.
       * @param type the desired target type
       * @param leadingArgCount number of fixed arguments, to be passed unchanged to the target
       * @return a method handle suitable for invoking any method handle of the given type
       * @throws NullPointerException if {@code type} is null
       * @throws IllegalArgumentException if {@code leadingArgCount} is not in
       *                  the range from 0 to {@code type.parameterCount()} inclusive,
       *                  or if the resulting method handle's type would have
       *          <a href="MethodHandle.html#maxarity">too many parameters</a>
       */
      static public
      MethodHandle spreadInvoker(MethodType type, int leadingArgCount) {
          if (leadingArgCount < 0 || leadingArgCount > type.parameterCount())
              throw newIllegalArgumentException("bad argument count", leadingArgCount);
  
          MethodHandle invoker = MethodHandles.invoker(type);
          int spreadArgCount = type.parameterCount() - leadingArgCount;
          invoker = invoker.asSpreader(Object[].class, spreadArgCount);
          return invoker;
      }
  
      /**
       * Produces a special <em>invoker method handle</em> which can be used to
       * invoke any method handle of the given type, as if by {@link MethodHandle#invokeExact invokeExact}.
       * The resulting invoker will have a type which is
       * exactly equal to the desired type, except that it will accept
       * an additional leading argument of type {@code MethodHandle}.
       * <p>
       * This method is equivalent to the following code (though it may be more efficient):
       * {@code publicLookup().findVirtual(MethodHandle.class, "invokeExact", type)}
       *
       * <p style="font-size:smaller;">
       * <em>Discussion:</em>
       * Invoker method handles can be useful when working with variable method handles
       * of unknown types.
       * For example, to emulate an {@code invokeExact} call to a variable method
       * handle {@code M}, extract its type {@code T},
       * look up the invoker method {@code X} for {@code T},
       * and call the invoker method, as {@code X.invoke(T, A...)}.
       * (It would not work to call {@code X.invokeExact}, since the type {@code T}
       * is unknown.)
       * If spreading, collecting, or other argument transformations are required,
       * they can be applied once to the invoker {@code X} and reused on many {@code M}
       * method handle values, as long as they are compatible with the type of {@code X}.
       * <p style="font-size:smaller;">
       * <em>(Note:  The invoker method is not available via the Core Reflection API.
       * An attempt to call {@linkplain Method#invoke java.lang.reflect.Method.invoke}
       * on the declared {@code invokeExact} or {@code invoke} method will raise an
       * {@link UnsupportedOperationException UnsupportedOperationException}.)</em>
       * <p>
       * This method throws no reflective or security exceptions.
       * @param type the desired target type
       * @return a method handle suitable for invoking any method handle of the given type
       * @throws IllegalArgumentException if the resulting method handle's type would have
       *          <a href="MethodHandle.html#maxarity">too many parameters</a>
       */
      static public
      MethodHandle exactInvoker(MethodType type) {
          return new Transformers.Invoker(type, true /* isExactInvoker */);
      }
  
      /**
       * Produces a special <em>invoker method handle</em> which can be used to
       * invoke any method handle compatible with the given type, as if by {@link MethodHandle#invoke invoke}.
       * The resulting invoker will have a type which is
       * exactly equal to the desired type, except that it will accept
       * an additional leading argument of type {@code MethodHandle}.
       * <p>
       * Before invoking its target, if the target differs from the expected type,
       * the invoker will apply reference casts as
       * necessary and box, unbox, or widen primitive values, as if by {@link MethodHandle#asType asType}.
       * Similarly, the return value will be converted as necessary.
       * If the target is a {@linkplain MethodHandle#asVarargsCollector variable arity method handle},
       * the required arity conversion will be made, again as if by {@link MethodHandle#asType asType}.
       * <p>
       * This method is equivalent to the following code (though it may be more efficient):
       * {@code publicLookup().findVirtual(MethodHandle.class, "invoke", type)}
       * <p style="font-size:smaller;">
       * <em>Discussion:</em>
       * A {@linkplain MethodType#genericMethodType general method type} is one which
       * mentions only {@code Object} arguments and return values.
       * An invoker for such a type is capable of calling any method handle
       * of the same arity as the general type.
       * <p style="font-size:smaller;">
       * <em>(Note:  The invoker method is not available via the Core Reflection API.
       * An attempt to call {@linkplain Method#invoke java.lang.reflect.Method.invoke}
       * on the declared {@code invokeExact} or {@code invoke} method will raise an
       * {@link UnsupportedOperationException UnsupportedOperationException}.)</em>
       * <p>
       * This method throws no reflective or security exceptions.
       * @param type the desired target type
       * @return a method handle suitable for invoking any method handle convertible to the given type
       * @throws IllegalArgumentException if the resulting method handle's type would have
       *          <a href="MethodHandle.html#maxarity">too many parameters</a>
       */
      static public
      MethodHandle invoker(MethodType type) {
          return new Transformers.Invoker(type, false /* isExactInvoker */);
      }
  
      // BEGIN Android-added: resolver for VarHandle accessor methods.
      static private MethodHandle methodHandleForVarHandleAccessor(VarHandle.AccessMode accessMode,
                                                                   MethodType type,
                                                                   boolean isExactInvoker) {
          Class<?> refc = VarHandle.class;
          Method method;
          try {
              method = refc.getDeclaredMethod(accessMode.methodName(), Object[].class);
          } catch (NoSuchMethodException e) {
              throw new InternalError("No method for AccessMode " + accessMode, e);
          }
          MethodType methodType = type.insertParameterTypes(0, VarHandle.class);
          int kind = isExactInvoker ? MethodHandle.INVOKE_VAR_HANDLE_EXACT
                                    : MethodHandle.INVOKE_VAR_HANDLE;
          return new MethodHandleImpl(method.getArtMethod(), kind, methodType);
      }
      // END Android-added: resolver for VarHandle accessor methods.
  
      /**
       * Produces a special <em>invoker method handle</em> which can be used to
       * invoke a signature-polymorphic access mode method on any VarHandle whose
       * associated access mode type is compatible with the given type.
       * The resulting invoker will have a type which is exactly equal to the
       * desired given type, except that it will accept an additional leading
       * argument of type {@code VarHandle}.
       *
       * @param accessMode the VarHandle access mode
       * @param type the desired target type
       * @return a method handle suitable for invoking an access mode method of
       *         any VarHandle whose access mode type is of the given type.
       * @since 9
       * @hide
       */
      static public
      MethodHandle varHandleExactInvoker(VarHandle.AccessMode accessMode, MethodType type) {
          return methodHandleForVarHandleAccessor(accessMode, type, true /* isExactInvoker */);
      }
  
      /**
       * Produces a special <em>invoker method handle</em> which can be used to
       * invoke a signature-polymorphic access mode method on any VarHandle whose
       * associated access mode type is compatible with the given type.
       * The resulting invoker will have a type which is exactly equal to the
       * desired given type, except that it will accept an additional leading
       * argument of type {@code VarHandle}.
       * <p>
       * Before invoking its target, if the access mode type differs from the
       * desired given type, the invoker will apply reference casts as necessary
       * and box, unbox, or widen primitive values, as if by
       * {@link MethodHandle#asType asType}.  Similarly, the return value will be
       * converted as necessary.
       * <p>
       * This method is equivalent to the following code (though it may be more
       * efficient): {@code publicLookup().findVirtual(VarHandle.class, accessMode.name(), type)}
       *
       * @param accessMode the VarHandle access mode
       * @param type the desired target type
       * @return a method handle suitable for invoking an access mode method of
       *         any VarHandle whose access mode type is convertible to the given
       *         type.
       * @since 9
       * @hide
       */
      static public
      MethodHandle varHandleInvoker(VarHandle.AccessMode accessMode, MethodType type) {
          return methodHandleForVarHandleAccessor(accessMode, type, false /* isExactInvoker */);
      }
  
      // Android-changed: Basic invokers are not supported.
      //
      // static /*non-public*/
      // MethodHandle basicInvoker(MethodType type) {
      //     return type.invokers().basicInvoker();
      // }
  
       /// method handle modification (creation from other method handles)
  
      /**
       * Produces a method handle which adapts the type of the
       * given method handle to a new type by pairwise argument and return type conversion.
       * The original type and new type must have the same number of arguments.
       * The resulting method handle is guaranteed to report a type
       * which is equal to the desired new type.
       * <p>
       * If the original type and new type are equal, returns target.
       * <p>
       * The same conversions are allowed as for {@link MethodHandle#asType MethodHandle.asType},
       * and some additional conversions are also applied if those conversions fail.
       * Given types <em>T0</em>, <em>T1</em>, one of the following conversions is applied
       * if possible, before or instead of any conversions done by {@code asType}:
       * <ul>
       * <li>If <em>T0</em> and <em>T1</em> are references, and <em>T1</em> is an interface type,
       *     then the value of type <em>T0</em> is passed as a <em>T1</em> without a cast.
       *     (This treatment of interfaces follows the usage of the bytecode verifier.)
       * <li>If <em>T0</em> is boolean and <em>T1</em> is another primitive,
       *     the boolean is converted to a byte value, 1 for true, 0 for false.
       *     (This treatment follows the usage of the bytecode verifier.)
       * <li>If <em>T1</em> is boolean and <em>T0</em> is another primitive,
       *     <em>T0</em> is converted to byte via Java casting conversion (JLS 5.5),
       *     and the low order bit of the result is tested, as if by {@code (x & 1) != 0}.
       * <li>If <em>T0</em> and <em>T1</em> are primitives other than boolean,
       *     then a Java casting conversion (JLS 5.5) is applied.
       *     (Specifically, <em>T0</em> will convert to <em>T1</em> by
       *     widening and/or narrowing.)
       * <li>If <em>T0</em> is a reference and <em>T1</em> a primitive, an unboxing
       *     conversion will be applied at runtime, possibly followed
       *     by a Java casting conversion (JLS 5.5) on the primitive value,
       *     possibly followed by a conversion from byte to boolean by testing
       *     the low-order bit.
       * <li>If <em>T0</em> is a reference and <em>T1</em> a primitive,
       *     and if the reference is null at runtime, a zero value is introduced.
       * </ul>
       * @param target the method handle to invoke after arguments are retyped
       * @param newType the expected type of the new method handle
       * @return a method handle which delegates to the target after performing
       *           any necessary argument conversions, and arranges for any
       *           necessary return value conversions
       * @throws NullPointerException if either argument is null
       * @throws WrongMethodTypeException if the conversion cannot be made
       * @see MethodHandle#asType
       */
      public static
      MethodHandle explicitCastArguments(MethodHandle target, MethodType newType) {
          explicitCastArgumentsChecks(target, newType);
          // use the asTypeCache when possible:
          MethodType oldType = target.type();
          if (oldType == newType) return target;
          if (oldType.explicitCastEquivalentToAsType(newType)) {
              if (Transformers.Transformer.class.isAssignableFrom(target.getClass())) {
                  // The StackFrameReader and StackFrameWriter used to perform transforms on
                  // EmulatedStackFrames (in Transformers.java) do not how to perform asType()
                  // conversions, but we know here that an explicit cast transform is the same as
                  // having called asType() on the method handle.
                  return new Transformers.ExplicitCastArguments(target.asFixedArity(), newType);
              } else {
                  // Runtime will perform asType() conversion during invocation.
                  return target.asFixedArity().asType(newType);
              }
          }
          return new Transformers.ExplicitCastArguments(target, newType);
      }
  
      private static void explicitCastArgumentsChecks(MethodHandle target, MethodType newType) {
          if (target.type().parameterCount() != newType.parameterCount()) {
              throw new WrongMethodTypeException("cannot explicitly cast " + target +
                                                 " to " + newType);
          }
      }
  
      /**
       * Produces a method handle which adapts the calling sequence of the
       * given method handle to a new type, by reordering the arguments.
       * The resulting method handle is guaranteed to report a type
       * which is equal to the desired new type.
       * <p>
       * The given array controls the reordering.
       * Call {@code #I} the number of incoming parameters (the value
       * {@code newType.parameterCount()}, and call {@code #O} the number
       * of outgoing parameters (the value {@code target.type().parameterCount()}).
       * Then the length of the reordering array must be {@code #O},
       * and each element must be a non-negative number less than {@code #I}.
       * For every {@code N} less than {@code #O}, the {@code N}-th
       * outgoing argument will be taken from the {@code I}-th incoming
       * argument, where {@code I} is {@code reorder[N]}.
       * <p>
       * No argument or return value conversions are applied.
       * The type of each incoming argument, as determined by {@code newType},
       * must be identical to the type of the corresponding outgoing parameter
       * or parameters in the target method handle.
       * The return type of {@code newType} must be identical to the return
       * type of the original target.
       * <p>
       * The reordering array need not specify an actual permutation.
       * An incoming argument will be duplicated if its index appears
       * more than once in the array, and an incoming argument will be dropped
       * if its index does not appear in the array.
       * As in the case of {@link #dropArguments(MethodHandle,int,List) dropArguments},
       * incoming arguments which are not mentioned in the reordering array
       * are may be any type, as determined only by {@code newType}.
       * <blockquote><pre>{@code
  import static java.lang.invoke.MethodHandles.*;
  import static java.lang.invoke.MethodType.*;
  ...
  MethodType intfn1 = methodType(int.class, int.class);
  MethodType intfn2 = methodType(int.class, int.class, int.class);
  MethodHandle sub = ... (int x, int y) -> (x-y) ...;
  assert(sub.type().equals(intfn2));
  MethodHandle sub1 = permuteArguments(sub, intfn2, 0, 1);
  MethodHandle rsub = permuteArguments(sub, intfn2, 1, 0);
  assert((int)rsub.invokeExact(1, 100) == 99);
  MethodHandle add = ... (int x, int y) -> (x+y) ...;
  assert(add.type().equals(intfn2));
  MethodHandle twice = permuteArguments(add, intfn1, 0, 0);
  assert(twice.type().equals(intfn1));
  assert((int)twice.invokeExact(21) == 42);
       * }</pre></blockquote>
       * @param target the method handle to invoke after arguments are reordered
       * @param newType the expected type of the new method handle
       * @param reorder an index array which controls the reordering
       * @return a method handle which delegates to the target after it
       *           drops unused arguments and moves and/or duplicates the other arguments
       * @throws NullPointerException if any argument is null
       * @throws IllegalArgumentException if the index array length is not equal to
       *                  the arity of the target, or if any index array element
       *                  not a valid index for a parameter of {@code newType},
       *                  or if two corresponding parameter types in
       *                  {@code target.type()} and {@code newType} are not identical,
       */
      public static
      MethodHandle permuteArguments(MethodHandle target, MethodType newType, int... reorder) {
          reorder = reorder.clone();  // get a private copy
          MethodType oldType = target.type();
          permuteArgumentChecks(reorder, newType, oldType);
  
          return new Transformers.PermuteArguments(newType, target, reorder);
      }
  
      // Android-changed: findFirstDupOrDrop is unused and removed.
      // private static int findFirstDupOrDrop(int[] reorder, int newArity);
  
      private static boolean permuteArgumentChecks(int[] reorder, MethodType newType, MethodType oldType) {
          if (newType.returnType() != oldType.returnType())
              throw newIllegalArgumentException("return types do not match",
                      oldType, newType);
          if (reorder.length == oldType.parameterCount()) {
              int limit = newType.parameterCount();
              boolean bad = false;
              for (int j = 0; j < reorder.length; j++) {
                  int i = reorder[j];
                  if (i < 0 || i >= limit) {
                      bad = true; break;
                  }
                  Class<?> src = newType.parameterType(i);
                  Class<?> dst = oldType.parameterType(j);
                  if (src != dst)
                      throw newIllegalArgumentException("parameter types do not match after reorder",
                              oldType, newType);
              }
              if (!bad)  return true;
          }
          throw newIllegalArgumentException("bad reorder array: "+Arrays.toString(reorder));
      }
  
      /**
       * Produces a method handle of the requested return type which returns the given
       * constant value every time it is invoked.
       * <p>
       * Before the method handle is returned, the passed-in value is converted to the requested type.
       * If the requested type is primitive, widening primitive conversions are attempted,
       * else reference conversions are attempted.
       * <p>The returned method handle is equivalent to {@code identity(type).bindTo(value)}.
       * @param type the return type of the desired method handle
       * @param value the value to return
       * @return a method handle of the given return type and no arguments, which always returns the given value
       * @throws NullPointerException if the {@code type} argument is null
       * @throws ClassCastException if the value cannot be converted to the required return type
       * @throws IllegalArgumentException if the given type is {@code void.class}
       */
      public static
      MethodHandle constant(Class<?> type, Object value) {
          if (type.isPrimitive()) {
              if (type == void.class)
                  throw newIllegalArgumentException("void type");
              Wrapper w = Wrapper.forPrimitiveType(type);
              value = w.convert(value, type);
          }
  
          return new Transformers.Constant(type, value);
      }
  
      /**
       * Produces a method handle which returns its sole argument when invoked.
       * @param type the type of the sole parameter and return value of the desired method handle
       * @return a unary method handle which accepts and returns the given type
       * @throws NullPointerException if the argument is null
       * @throws IllegalArgumentException if the given type is {@code void.class}
       */
      public static
      MethodHandle identity(Class<?> type) {
          if (type == null) {
              throw new NullPointerException("type == null");
          }
  
          if (type.isPrimitive()) {
              try {
                  return Lookup.PUBLIC_LOOKUP.findStatic(MethodHandles.class, "identity",
                          MethodType.methodType(type, type));
              } catch (NoSuchMethodException | IllegalAccessException e) {
                  throw new AssertionError(e);
              }
          }
  
          return new Transformers.ReferenceIdentity(type);
      }
  
      /** @hide */ public static byte identity(byte val) { return val; }
      /** @hide */ public static boolean identity(boolean val) { return val; }
      /** @hide */ public static char identity(char val) { return val; }
      /** @hide */ public static short identity(short val) { return val; }
      /** @hide */ public static int identity(int val) { return val; }
      /** @hide */ public static long identity(long val) { return val; }
      /** @hide */ public static float identity(float val) { return val; }
      /** @hide */ public static double identity(double val) { return val; }
  
      /**
       * Provides a target method handle with one or more <em>bound arguments</em>
       * in advance of the method handle's invocation.
       * The formal parameters to the target corresponding to the bound
       * arguments are called <em>bound parameters</em>.
       * Returns a new method handle which saves away the bound arguments.
       * When it is invoked, it receives arguments for any non-bound parameters,
       * binds the saved arguments to their corresponding parameters,
       * and calls the original target.
       * <p>
       * The type of the new method handle will drop the types for the bound
       * parameters from the original target type, since the new method handle
       * will no longer require those arguments to be supplied by its callers.
       * <p>
       * Each given argument object must match the corresponding bound parameter type.
       * If a bound parameter type is a primitive, the argument object
       * must be a wrapper, and will be unboxed to produce the primitive value.
       * <p>
       * The {@code pos} argument selects which parameters are to be bound.
       * It may range between zero and <i>N-L</i> (inclusively),
       * where <i>N</i> is the arity of the target method handle
       * and <i>L</i> is the length of the values array.
       * @param target the method handle to invoke after the argument is inserted
       * @param pos where to insert the argument (zero for the first)
       * @param values the series of arguments to insert
       * @return a method handle which inserts an additional argument,
       *         before calling the original method handle
       * @throws NullPointerException if the target or the {@code values} array is null
       * @see MethodHandle#bindTo
       */
      public static
      MethodHandle insertArguments(MethodHandle target, int pos, Object... values) {
          int insCount = values.length;
          Class<?>[] ptypes = insertArgumentsChecks(target, insCount, pos);
          if (insCount == 0)  {
              return target;
          }
  
          // Throw ClassCastExceptions early if we can't cast any of the provided values
          // to the required type.
          for (int i = 0; i < insCount; i++) {
              final Class<?> ptype = ptypes[pos + i];
              if (!ptype.isPrimitive()) {
                  ptypes[pos + i].cast(values[i]);
              } else {
                  // Will throw a ClassCastException if something terrible happens.
                  values[i] = Wrapper.forPrimitiveType(ptype).convert(values[i], ptype);
              }
          }
  
          return new Transformers.InsertArguments(target, pos, values);
      }
  
      // Android-changed: insertArgumentPrimitive is unused.
      //
      // private static BoundMethodHandle insertArgumentPrimitive(BoundMethodHandle result, int pos,
      //                                                          Class<?> ptype, Object value) {
      //     Wrapper w = Wrapper.forPrimitiveType(ptype);
      //     // perform unboxing and/or primitive conversion
      //     value = w.convert(value, ptype);
      //     switch (w) {
      //     case INT:     return result.bindArgumentI(pos, (int)value);
      //     case LONG:    return result.bindArgumentJ(pos, (long)value);
      //     case FLOAT:   return result.bindArgumentF(pos, (float)value);
      //     case DOUBLE:  return result.bindArgumentD(pos, (double)value);
      //     default:      return result.bindArgumentI(pos, ValueConversions.widenSubword(value));
      //     }
      // }
  
      private static Class<?>[] insertArgumentsChecks(MethodHandle target, int insCount, int pos) throws RuntimeException {
          MethodType oldType = target.type();
          int outargs = oldType.parameterCount();
          int inargs  = outargs - insCount;
          if (inargs < 0)
              throw newIllegalArgumentException("too many values to insert");
          if (pos < 0 || pos > inargs)
              throw newIllegalArgumentException("no argument type to append");
          return oldType.ptypes();
      }
  
      /**
       * Produces a method handle which will discard some dummy arguments
       * before calling some other specified <i>target</i> method handle.
       * The type of the new method handle will be the same as the target's type,
       * except it will also include the dummy argument types,
       * at some given position.
       * <p>
       * The {@code pos} argument may range between zero and <i>N</i>,
       * where <i>N</i> is the arity of the target.
       * If {@code pos} is zero, the dummy arguments will precede
       * the target's real arguments; if {@code pos} is <i>N</i>
       * they will come after.
       * <p>
       * <b>Example:</b>
       * <blockquote><pre>{@code
  import static java.lang.invoke.MethodHandles.*;
  import static java.lang.invoke.MethodType.*;
  ...
  MethodHandle cat = lookup().findVirtual(String.class,
    "concat", methodType(String.class, String.class));
  assertEquals("xy", (String) cat.invokeExact("x", "y"));
  MethodType bigType = cat.type().insertParameterTypes(0, int.class, String.class);
  MethodHandle d0 = dropArguments(cat, 0, bigType.parameterList().subList(0,2));
  assertEquals(bigType, d0.type());
  assertEquals("yz", (String) d0.invokeExact(123, "x", "y", "z"));
       * }</pre></blockquote>
       * <p>
       * This method is also equivalent to the following code:
       * <blockquote><pre>
       * {@link #dropArguments(MethodHandle,int,Class...) dropArguments}{@code (target, pos, valueTypes.toArray(new Class[0]))}
       * </pre></blockquote>
       * @param target the method handle to invoke after the arguments are dropped
       * @param valueTypes the type(s) of the argument(s) to drop
       * @param pos position of first argument to drop (zero for the leftmost)
       * @return a method handle which drops arguments of the given types,
       *         before calling the original method handle
       * @throws NullPointerException if the target is null,
       *                              or if the {@code valueTypes} list or any of its elements is null
       * @throws IllegalArgumentException if any element of {@code valueTypes} is {@code void.class},
       *                  or if {@code pos} is negative or greater than the arity of the target,
       *                  or if the new method handle's type would have too many parameters
       */
      public static
      MethodHandle dropArguments(MethodHandle target, int pos, List<Class<?>> valueTypes) {
          valueTypes = copyTypes(valueTypes);
          MethodType oldType = target.type();  // get NPE
          int dropped = dropArgumentChecks(oldType, pos, valueTypes);
  
          MethodType newType = oldType.insertParameterTypes(pos, valueTypes);
          if (dropped == 0) {
              return target;
          }
  
          return new Transformers.DropArguments(newType, target, pos, valueTypes.size());
      }
  
      private static List<Class<?>> copyTypes(List<Class<?>> types) {
          Object[] a = types.toArray();
          return Arrays.asList(Arrays.copyOf(a, a.length, Class[].class));
      }
  
      private static int dropArgumentChecks(MethodType oldType, int pos, List<Class<?>> valueTypes) {
          int dropped = valueTypes.size();
          MethodType.checkSlotCount(dropped);
          int outargs = oldType.parameterCount();
          int inargs  = outargs + dropped;
          if (pos < 0 || pos > outargs)
              throw newIllegalArgumentException("no argument type to remove"
                      + Arrays.asList(oldType, pos, valueTypes, inargs, outargs)
                      );
          return dropped;
      }
  
      /**
       * Produces a method handle which will discard some dummy arguments
       * before calling some other specified <i>target</i> method handle.
       * The type of the new method handle will be the same as the target's type,
       * except it will also include the dummy argument types,
       * at some given position.
       * <p>
       * The {@code pos} argument may range between zero and <i>N</i>,
       * where <i>N</i> is the arity of the target.
       * If {@code pos} is zero, the dummy arguments will precede
       * the target's real arguments; if {@code pos} is <i>N</i>
       * they will come after.
       * <p>
       * <b>Example:</b>
       * <blockquote><pre>{@code
  import static java.lang.invoke.MethodHandles.*;
  import static java.lang.invoke.MethodType.*;
  ...
  MethodHandle cat = lookup().findVirtual(String.class,
    "concat", methodType(String.class, String.class));
  assertEquals("xy", (String) cat.invokeExact("x", "y"));
  MethodHandle d0 = dropArguments(cat, 0, String.class);
  assertEquals("yz", (String) d0.invokeExact("x", "y", "z"));
  MethodHandle d1 = dropArguments(cat, 1, String.class);
  assertEquals("xz", (String) d1.invokeExact("x", "y", "z"));
  MethodHandle d2 = dropArguments(cat, 2, String.class);
  assertEquals("xy", (String) d2.invokeExact("x", "y", "z"));
  MethodHandle d12 = dropArguments(cat, 1, int.class, boolean.class);
  assertEquals("xz", (String) d12.invokeExact("x", 12, true, "z"));
       * }</pre></blockquote>
       * <p>
       * This method is also equivalent to the following code:
       * <blockquote><pre>
       * {@link #dropArguments(MethodHandle,int,List) dropArguments}{@code (target, pos, Arrays.asList(valueTypes))}
       * </pre></blockquote>
       * @param target the method handle to invoke after the arguments are dropped
       * @param valueTypes the type(s) of the argument(s) to drop
       * @param pos position of first argument to drop (zero for the leftmost)
       * @return a method handle which drops arguments of the given types,
       *         before calling the original method handle
       * @throws NullPointerException if the target is null,
       *                              or if the {@code valueTypes} array or any of its elements is null
       * @throws IllegalArgumentException if any element of {@code valueTypes} is {@code void.class},
       *                  or if {@code pos} is negative or greater than the arity of the target,
       *                  or if the new method handle's type would have
       *                  <a href="MethodHandle.html#maxarity">too many parameters</a>
       */
      public static
      MethodHandle dropArguments(MethodHandle target, int pos, Class<?>... valueTypes) {
          return dropArguments(target, pos, Arrays.asList(valueTypes));
      }
  
      /**
       * Adapts a target method handle by pre-processing
       * one or more of its arguments, each with its own unary filter function,
       * and then calling the target with each pre-processed argument
       * replaced by the result of its corresponding filter function.
       * <p>
       * The pre-processing is performed by one or more method handles,
       * specified in the elements of the {@code filters} array.
       * The first element of the filter array corresponds to the {@code pos}
       * argument of the target, and so on in sequence.
       * <p>
       * Null arguments in the array are treated as identity functions,
       * and the corresponding arguments left unchanged.
       * (If there are no non-null elements in the array, the original target is returned.)
       * Each filter is applied to the corresponding argument of the adapter.
       * <p>
       * If a filter {@code F} applies to the {@code N}th argument of
       * the target, then {@code F} must be a method handle which
       * takes exactly one argument.  The type of {@code F}'s sole argument
       * replaces the corresponding argument type of the target
       * in the resulting adapted method handle.
       * The return type of {@code F} must be identical to the corresponding
       * parameter type of the target.
       * <p>
       * It is an error if there are elements of {@code filters}
       * (null or not)
       * which do not correspond to argument positions in the target.
       * <p><b>Example:</b>
       * <blockquote><pre>{@code
  import static java.lang.invoke.MethodHandles.*;
  import static java.lang.invoke.MethodType.*;
  ...
  MethodHandle cat = lookup().findVirtual(String.class,
    "concat", methodType(String.class, String.class));
  MethodHandle upcase = lookup().findVirtual(String.class,
    "toUpperCase", methodType(String.class));
  assertEquals("xy", (String) cat.invokeExact("x", "y"));
  MethodHandle f0 = filterArguments(cat, 0, upcase);
  assertEquals("Xy", (String) f0.invokeExact("x", "y")); // Xy
  MethodHandle f1 = filterArguments(cat, 1, upcase);
  assertEquals("xY", (String) f1.invokeExact("x", "y")); // xY
  MethodHandle f2 = filterArguments(cat, 0, upcase, upcase);
  assertEquals("XY", (String) f2.invokeExact("x", "y")); // XY
       * }</pre></blockquote>
       * <p> Here is pseudocode for the resulting adapter:
       * <blockquote><pre>{@code
       * V target(P... p, A[i]... a[i], B... b);
       * A[i] filter[i](V[i]);
       * T adapter(P... p, V[i]... v[i], B... b) {
       *   return target(p..., f[i](v[i])..., b...);
       * }
       * }</pre></blockquote>
       *
       * @param target the method handle to invoke after arguments are filtered
       * @param pos the position of the first argument to filter
       * @param filters method handles to call initially on filtered arguments
       * @return method handle which incorporates the specified argument filtering logic
       * @throws NullPointerException if the target is null
       *                              or if the {@code filters} array is null
       * @throws IllegalArgumentException if a non-null element of {@code filters}
       *          does not match a corresponding argument type of target as described above,
       *          or if the {@code pos+filters.length} is greater than {@code target.type().parameterCount()},
       *          or if the resulting method handle's type would have
       *          <a href="MethodHandle.html#maxarity">too many parameters</a>
       */
      public static
      MethodHandle filterArguments(MethodHandle target, int pos, MethodHandle... filters) {
          filterArgumentsCheckArity(target, pos, filters);
  
          for (int i = 0; i < filters.length; ++i) {
              filterArgumentChecks(target, i + pos, filters[i]);
          }
  
          return new Transformers.FilterArguments(target, pos, filters);
      }
  
      private static void filterArgumentsCheckArity(MethodHandle target, int pos, MethodHandle[] filters) {
          MethodType targetType = target.type();
          int maxPos = targetType.parameterCount();
          if (pos + filters.length > maxPos)
              throw newIllegalArgumentException("too many filters");
      }
  
      private static void filterArgumentChecks(MethodHandle target, int pos, MethodHandle filter) throws RuntimeException {
          MethodType targetType = target.type();
          MethodType filterType = filter.type();
          if (filterType.parameterCount() != 1
              || filterType.returnType() != targetType.parameterType(pos))
              throw newIllegalArgumentException("target and filter types do not match", targetType, filterType);
      }
  
      /**
       * Adapts a target method handle by pre-processing
       * a sub-sequence of its arguments with a filter (another method handle).
       * The pre-processed arguments are replaced by the result (if any) of the
       * filter function.
       * The target is then called on the modified (usually shortened) argument list.
       * <p>
       * If the filter returns a value, the target must accept that value as
       * its argument in position {@code pos}, preceded and/or followed by
       * any arguments not passed to the filter.
       * If the filter returns void, the target must accept all arguments
       * not passed to the filter.
       * No arguments are reordered, and a result returned from the filter
       * replaces (in order) the whole subsequence of arguments originally
       * passed to the adapter.
       * <p>
       * The argument types (if any) of the filter
       * replace zero or one argument types of the target, at position {@code pos},
       * in the resulting adapted method handle.
       * The return type of the filter (if any) must be identical to the
       * argument type of the target at position {@code pos}, and that target argument
       * is supplied by the return value of the filter.
       * <p>
       * In all cases, {@code pos} must be greater than or equal to zero, and
       * {@code pos} must also be less than or equal to the target's arity.
       * <p><b>Example:</b>
       * <blockquote><pre>{@code
  import static java.lang.invoke.MethodHandles.*;
  import static java.lang.invoke.MethodType.*;
  ...
  MethodHandle deepToString = publicLookup()
    .findStatic(Arrays.class, "deepToString", methodType(String.class, Object[].class));
  
  MethodHandle ts1 = deepToString.asCollector(String[].class, 1);
  assertEquals("[strange]", (String) ts1.invokeExact("strange"));
  
  MethodHandle ts2 = deepToString.asCollector(String[].class, 2);
  assertEquals("[up, down]", (String) ts2.invokeExact("up", "down"));
  
  MethodHandle ts3 = deepToString.asCollector(String[].class, 3);
  MethodHandle ts3_ts2 = collectArguments(ts3, 1, ts2);
  assertEquals("[top, [up, down], strange]",
               (String) ts3_ts2.invokeExact("top", "up", "down", "strange"));
  
  MethodHandle ts3_ts2_ts1 = collectArguments(ts3_ts2, 3, ts1);
  assertEquals("[top, [up, down], [strange]]",
               (String) ts3_ts2_ts1.invokeExact("top", "up", "down", "strange"));
  
  MethodHandle ts3_ts2_ts3 = collectArguments(ts3_ts2, 1, ts3);
  assertEquals("[top, [[up, down, strange], charm], bottom]",
               (String) ts3_ts2_ts3.invokeExact("top", "up", "down", "strange", "charm", "bottom"));
       * }</pre></blockquote>
       * <p> Here is pseudocode for the resulting adapter:
       * <blockquote><pre>{@code
       * T target(A...,V,C...);
       * V filter(B...);
       * T adapter(A... a,B... b,C... c) {
       *   V v = filter(b...);
       *   return target(a...,v,c...);
       * }
       * // and if the filter has no arguments:
       * T target2(A...,V,C...);
       * V filter2();
       * T adapter2(A... a,C... c) {
       *   V v = filter2();
       *   return target2(a...,v,c...);
       * }
       * // and if the filter has a void return:
       * T target3(A...,C...);
       * void filter3(B...);
       * void adapter3(A... a,B... b,C... c) {
       *   filter3(b...);
       *   return target3(a...,c...);
       * }
       * }</pre></blockquote>
       * <p>
       * A collection adapter {@code collectArguments(mh, 0, coll)} is equivalent to
       * one which first "folds" the affected arguments, and then drops them, in separate
       * steps as follows:
       * <blockquote><pre>{@code
       * mh = MethodHandles.dropArguments(mh, 1, coll.type().parameterList()); //step 2
       * mh = MethodHandles.foldArguments(mh, coll); //step 1
       * }</pre></blockquote>
       * If the target method handle consumes no arguments besides than the result
       * (if any) of the filter {@code coll}, then {@code collectArguments(mh, 0, coll)}
       * is equivalent to {@code filterReturnValue(coll, mh)}.
       * If the filter method handle {@code coll} consumes one argument and produces
       * a non-void result, then {@code collectArguments(mh, N, coll)}
       * is equivalent to {@code filterArguments(mh, N, coll)}.
       * Other equivalences are possible but would require argument permutation.
       *
       * @param target the method handle to invoke after filtering the subsequence of arguments
       * @param pos the position of the first adapter argument to pass to the filter,
       *            and/or the target argument which receives the result of the filter
       * @param filter method handle to call on the subsequence of arguments
       * @return method handle which incorporates the specified argument subsequence filtering logic
       * @throws NullPointerException if either argument is null
       * @throws IllegalArgumentException if the return type of {@code filter}
       *          is non-void and is not the same as the {@code pos} argument of the target,
       *          or if {@code pos} is not between 0 and the target's arity, inclusive,
       *          or if the resulting method handle's type would have
       *          <a href="MethodHandle.html#maxarity">too many parameters</a>
       * @see MethodHandles#foldArguments
       * @see MethodHandles#filterArguments
       * @see MethodHandles#filterReturnValue
       */
      public static
      MethodHandle collectArguments(MethodHandle target, int pos, MethodHandle filter) {
          MethodType newType = collectArgumentsChecks(target, pos, filter);
          return new Transformers.CollectArguments(target, filter, pos, newType);
      }
  
      private static MethodType collectArgumentsChecks(MethodHandle target, int pos, MethodHandle filter) throws RuntimeException {
          MethodType targetType = target.type();
          MethodType filterType = filter.type();
          Class<?> rtype = filterType.returnType();
          List<Class<?>> filterArgs = filterType.parameterList();
          if (rtype == void.class) {
              return targetType.insertParameterTypes(pos, filterArgs);
          }
          if (rtype != targetType.parameterType(pos)) {
              throw newIllegalArgumentException("target and filter types do not match", targetType, filterType);
          }
          return targetType.dropParameterTypes(pos, pos+1).insertParameterTypes(pos, filterArgs);
      }
  
      /**
       * Adapts a target method handle by post-processing
       * its return value (if any) with a filter (another method handle).
       * The result of the filter is returned from the adapter.
       * <p>
       * If the target returns a value, the filter must accept that value as
       * its only argument.
       * If the target returns void, the filter must accept no arguments.
       * <p>
       * The return type of the filter
       * replaces the return type of the target
       * in the resulting adapted method handle.
       * The argument type of the filter (if any) must be identical to the
       * return type of the target.
       * <p><b>Example:</b>
       * <blockquote><pre>{@code
  import static java.lang.invoke.MethodHandles.*;
  import static java.lang.invoke.MethodType.*;
  ...
  MethodHandle cat = lookup().findVirtual(String.class,
    "concat", methodType(String.class, String.class));
  MethodHandle length = lookup().findVirtual(String.class,
    "length", methodType(int.class));
  System.out.println((String) cat.invokeExact("x", "y")); // xy
  MethodHandle f0 = filterReturnValue(cat, length);
  System.out.println((int) f0.invokeExact("x", "y")); // 2
       * }</pre></blockquote>
       * <p> Here is pseudocode for the resulting adapter:
       * <blockquote><pre>{@code
       * V target(A...);
       * T filter(V);
       * T adapter(A... a) {
       *   V v = target(a...);
       *   return filter(v);
       * }
       * // and if the target has a void return:
       * void target2(A...);
       * T filter2();
       * T adapter2(A... a) {
       *   target2(a...);
       *   return filter2();
       * }
       * // and if the filter has a void return:
       * V target3(A...);
       * void filter3(V);
       * void adapter3(A... a) {
       *   V v = target3(a...);
       *   filter3(v);
       * }
       * }</pre></blockquote>
       * @param target the method handle to invoke before filtering the return value
       * @param filter method handle to call on the return value
       * @return method handle which incorporates the specified return value filtering logic
       * @throws NullPointerException if either argument is null
       * @throws IllegalArgumentException if the argument list of {@code filter}
       *          does not match the return type of target as described above
       */
      public static
      MethodHandle filterReturnValue(MethodHandle target, MethodHandle filter) {
          MethodType targetType = target.type();
          MethodType filterType = filter.type();
          filterReturnValueChecks(targetType, filterType);
  
          return new Transformers.FilterReturnValue(target, filter);
      }
  
      private static void filterReturnValueChecks(MethodType targetType, MethodType filterType) throws RuntimeException {
          Class<?> rtype = targetType.returnType();
          int filterValues = filterType.parameterCount();
          if (filterValues == 0
                  ? (rtype != void.class)
                  : (rtype != filterType.parameterType(0) || filterValues != 1))
              throw newIllegalArgumentException("target and filter types do not match", targetType, filterType);
      }
  
      /**
       * Adapts a target method handle by pre-processing
       * some of its arguments, and then calling the target with
       * the result of the pre-processing, inserted into the original
       * sequence of arguments.
       * <p>
       * The pre-processing is performed by {@code combiner}, a second method handle.
       * Of the arguments passed to the adapter, the first {@code N} arguments
       * are copied to the combiner, which is then called.
       * (Here, {@code N} is defined as the parameter count of the combiner.)
       * After this, control passes to the target, with any result
       * from the combiner inserted before the original {@code N} incoming
       * arguments.
       * <p>
       * If the combiner returns a value, the first parameter type of the target
       * must be identical with the return type of the combiner, and the next
       * {@code N} parameter types of the target must exactly match the parameters
       * of the combiner.
       * <p>
       * If the combiner has a void return, no result will be inserted,
       * and the first {@code N} parameter types of the target
       * must exactly match the parameters of the combiner.
       * <p>
       * The resulting adapter is the same type as the target, except that the
       * first parameter type is dropped,
       * if it corresponds to the result of the combiner.
       * <p>
       * (Note that {@link #dropArguments(MethodHandle,int,List) dropArguments} can be used to remove any arguments
       * that either the combiner or the target does not wish to receive.
       * If some of the incoming arguments are destined only for the combiner,
       * consider using {@link MethodHandle#asCollector asCollector} instead, since those
       * arguments will not need to be live on the stack on entry to the
       * target.)
       * <p><b>Example:</b>
       * <blockquote><pre>{@code
  import static java.lang.invoke.MethodHandles.*;
  import static java.lang.invoke.MethodType.*;
  ...
  MethodHandle trace = publicLookup().findVirtual(java.io.PrintStream.class,
    "println", methodType(void.class, String.class))
      .bindTo(System.out);
  MethodHandle cat = lookup().findVirtual(String.class,
    "concat", methodType(String.class, String.class));
  assertEquals("boojum", (String) cat.invokeExact("boo", "jum"));
  MethodHandle catTrace = foldArguments(cat, trace);
  // also prints "boo":
  assertEquals("boojum", (String) catTrace.invokeExact("boo", "jum"));
       * }</pre></blockquote>
       * <p> Here is pseudocode for the resulting adapter:
       * <blockquote><pre>{@code
       * // there are N arguments in A...
       * T target(V, A[N]..., B...);
       * V combiner(A...);
       * T adapter(A... a, B... b) {
       *   V v = combiner(a...);
       *   return target(v, a..., b...);
       * }
       * // and if the combiner has a void return:
       * T target2(A[N]..., B...);
       * void combiner2(A...);
       * T adapter2(A... a, B... b) {
       *   combiner2(a...);
       *   return target2(a..., b...);
       * }
       * }</pre></blockquote>
       * @param target the method handle to invoke after arguments are combined
       * @param combiner method handle to call initially on the incoming arguments
       * @return method handle which incorporates the specified argument folding logic
       * @throws NullPointerException if either argument is null
       * @throws IllegalArgumentException if {@code combiner}'s return type
       *          is non-void and not the same as the first argument type of
       *          the target, or if the initial {@code N} argument types
       *          of the target
       *          (skipping one matching the {@code combiner}'s return type)
       *          are not identical with the argument types of {@code combiner}
       */
      public static
      MethodHandle foldArguments(MethodHandle target, MethodHandle combiner) {
          int foldPos = 0;
          MethodType targetType = target.type();
          MethodType combinerType = combiner.type();
          Class<?> rtype = foldArgumentChecks(foldPos, targetType, combinerType);
  
          return new Transformers.FoldArguments(target, combiner);
      }
  
      private static Class<?> foldArgumentChecks(int foldPos, MethodType targetType, MethodType combinerType) {
          int foldArgs   = combinerType.parameterCount();
          Class<?> rtype = combinerType.returnType();
          int foldVals = rtype == void.class ? 0 : 1;
          int afterInsertPos = foldPos + foldVals;
          boolean ok = (targetType.parameterCount() >= afterInsertPos + foldArgs);
          if (ok && !(combinerType.parameterList()
                      .equals(targetType.parameterList().subList(afterInsertPos,
                                                                 afterInsertPos + foldArgs))))
              ok = false;
          if (ok && foldVals != 0 && combinerType.returnType() != targetType.parameterType(0))
              ok = false;
          if (!ok)
              throw misMatchedTypes("target and combiner types", targetType, combinerType);
          return rtype;
      }
  
      /**
       * Makes a method handle which adapts a target method handle,
       * by guarding it with a test, a boolean-valued method handle.
       * If the guard fails, a fallback handle is called instead.
       * All three method handles must have the same corresponding
       * argument and return types, except that the return type
       * of the test must be boolean, and the test is allowed
       * to have fewer arguments than the other two method handles.
       * <p> Here is pseudocode for the resulting adapter:
       * <blockquote><pre>{@code
       * boolean test(A...);
       * T target(A...,B...);
       * T fallback(A...,B...);
       * T adapter(A... a,B... b) {
       *   if (test(a...))
       *     return target(a..., b...);
       *   else
       *     return fallback(a..., b...);
       * }
       * }</pre></blockquote>
       * Note that the test arguments ({@code a...} in the pseudocode) cannot
       * be modified by execution of the test, and so are passed unchanged
       * from the caller to the target or fallback as appropriate.
       * @param test method handle used for test, must return boolean
       * @param target method handle to call if test passes
       * @param fallback method handle to call if test fails
       * @return method handle which incorporates the specified if/then/else logic
       * @throws NullPointerException if any argument is null
       * @throws IllegalArgumentException if {@code test} does not return boolean,
       *          or if all three method types do not match (with the return
       *          type of {@code test} changed to match that of the target).
       */
      public static
      MethodHandle guardWithTest(MethodHandle test,
                                 MethodHandle target,
                                 MethodHandle fallback) {
          MethodType gtype = test.type();
          MethodType ttype = target.type();
          MethodType ftype = fallback.type();
          if (!ttype.equals(ftype))
              throw misMatchedTypes("target and fallback types", ttype, ftype);
          if (gtype.returnType() != boolean.class)
              throw newIllegalArgumentException("guard type is not a predicate "+gtype);
          List<Class<?>> targs = ttype.parameterList();
          List<Class<?>> gargs = gtype.parameterList();
          if (!targs.equals(gargs)) {
              int gpc = gargs.size(), tpc = targs.size();
              if (gpc >= tpc || !targs.subList(0, gpc).equals(gargs))
                  throw misMatchedTypes("target and test types", ttype, gtype);
              test = dropArguments(test, gpc, targs.subList(gpc, tpc));
              gtype = test.type();
          }
  
          return new Transformers.GuardWithTest(test, target, fallback);
      }
  
      static RuntimeException misMatchedTypes(String what, MethodType t1, MethodType t2) {
          return newIllegalArgumentException(what + " must match: " + t1 + " != " + t2);
      }
  
      /**
       * Makes a method handle which adapts a target method handle,
       * by running it inside an exception handler.
       * If the target returns normally, the adapter returns that value.
       * If an exception matching the specified type is thrown, the fallback
       * handle is called instead on the exception, plus the original arguments.
       * <p>
       * The target and handler must have the same corresponding
       * argument and return types, except that handler may omit trailing arguments
       * (similarly to the predicate in {@link #guardWithTest guardWithTest}).
       * Also, the handler must have an extra leading parameter of {@code exType} or a supertype.
       * <p> Here is pseudocode for the resulting adapter:
       * <blockquote><pre>{@code
       * T target(A..., B...);
       * T handler(ExType, A...);
       * T adapter(A... a, B... b) {
       *   try {
       *     return target(a..., b...);
       *   } catch (ExType ex) {
       *     return handler(ex, a...);
       *   }
       * }
       * }</pre></blockquote>
       * Note that the saved arguments ({@code a...} in the pseudocode) cannot
       * be modified by execution of the target, and so are passed unchanged
       * from the caller to the handler, if the handler is invoked.
       * <p>
       * The target and handler must return the same type, even if the handler
       * always throws.  (This might happen, for instance, because the handler
       * is simulating a {@code finally} clause).
       * To create such a throwing handler, compose the handler creation logic
       * with {@link #throwException throwException},
       * in order to create a method handle of the correct return type.
       * @param target method handle to call
       * @param exType the type of exception which the handler will catch
       * @param handler method handle to call if a matching exception is thrown
       * @return method handle which incorporates the specified try/catch logic
       * @throws NullPointerException if any argument is null
       * @throws IllegalArgumentException if {@code handler} does not accept
       *          the given exception type, or if the method handle types do
       *          not match in their return types and their
       *          corresponding parameters
       */
      public static
      MethodHandle catchException(MethodHandle target,
                                  Class<? extends Throwable> exType,
                                  MethodHandle handler) {
          MethodType ttype = target.type();
          MethodType htype = handler.type();
          if (htype.parameterCount() < 1 ||
              !htype.parameterType(0).isAssignableFrom(exType))
              throw newIllegalArgumentException("handler does not accept exception type "+exType);
          if (htype.returnType() != ttype.returnType())
              throw misMatchedTypes("target and handler return types", ttype, htype);
          List<Class<?>> targs = ttype.parameterList();
          List<Class<?>> hargs = htype.parameterList();
          hargs = hargs.subList(1, hargs.size());  // omit leading parameter from handler
          if (!targs.equals(hargs)) {
              int hpc = hargs.size(), tpc = targs.size();
              if (hpc >= tpc || !targs.subList(0, hpc).equals(hargs))
                  throw misMatchedTypes("target and handler types", ttype, htype);
          }
  
          return new Transformers.CatchException(target, handler, exType);
      }
  
      /**
       * Produces a method handle which will throw exceptions of the given {@code exType}.
       * The method handle will accept a single argument of {@code exType},
       * and immediately throw it as an exception.
       * The method type will nominally specify a return of {@code returnType}.
       * The return type may be anything convenient:  It doesn't matter to the
       * method handle's behavior, since it will never return normally.
       * @param returnType the return type of the desired method handle
       * @param exType the parameter type of the desired method handle
       * @return method handle which can throw the given exceptions
       * @throws NullPointerException if either argument is null
       */
      public static
      MethodHandle throwException(Class<?> returnType, Class<? extends Throwable> exType) {
          if (!Throwable.class.isAssignableFrom(exType))
              throw new ClassCastException(exType.getName());
  
          return new Transformers.AlwaysThrow(returnType, exType);
      }
  }
  