content: /*
   * Copyright (c) 2008, 2013, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle in the LICENSE file that accompanied this code.
   *
   * 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
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  
  package java.lang.invoke;
  
  
  import dalvik.system.EmulatedStackFrame;
  
  import static java.lang.invoke.MethodHandleStatics.*;
  
  /**
   * A method handle is a typed, directly executable reference to an underlying method,
   * constructor, field, or similar low-level operation, with optional
   * transformations of arguments or return values.
   * These transformations are quite general, and include such patterns as
   * {@linkplain #asType conversion},
   * {@linkplain #bindTo insertion},
   * {@linkplain MethodHandles#dropArguments deletion},
   * and {@linkplain MethodHandles#filterArguments substitution}.
   *
   * <h1>Method handle contents</h1>
   * Method handles are dynamically and strongly typed according to their parameter and return types.
   * They are not distinguished by the name or the defining class of their underlying methods.
   * A method handle must be invoked using a symbolic type descriptor which matches
   * the method handle's own {@linkplain #type type descriptor}.
   * <p>
   * Every method handle reports its type descriptor via the {@link #type type} accessor.
   * This type descriptor is a {@link MethodType MethodType} object,
   * whose structure is a series of classes, one of which is
   * the return type of the method (or {@code void.class} if none).
   * <p>
   * A method handle's type controls the types of invocations it accepts,
   * and the kinds of transformations that apply to it.
   * <p>
   * A method handle contains a pair of special invoker methods
   * called {@link #invokeExact invokeExact} and {@link #invoke invoke}.
   * Both invoker methods provide direct access to the method handle's
   * underlying method, constructor, field, or other operation,
   * as modified by transformations of arguments and return values.
   * Both invokers accept calls which exactly match the method handle's own type.
   * The plain, inexact invoker also accepts a range of other call types.
   * <p>
   * Method handles are immutable and have no visible state.
   * Of course, they can be bound to underlying methods or data which exhibit state.
   * With respect to the Java Memory Model, any method handle will behave
   * as if all of its (internal) fields are final variables.  This means that any method
   * handle made visible to the application will always be fully formed.
   * This is true even if the method handle is published through a shared
   * variable in a data race.
   * <p>
   * Method handles cannot be subclassed by the user.
   * Implementations may (or may not) create internal subclasses of {@code MethodHandle}
   * which may be visible via the {@link Object#getClass Object.getClass}
   * operation.  The programmer should not draw conclusions about a method handle
   * from its specific class, as the method handle class hierarchy (if any)
   * may change from time to time or across implementations from different vendors.
   *
   * <h1>Method handle compilation</h1>
   * A Java method call expression naming {@code invokeExact} or {@code invoke}
   * can invoke a method handle from Java source code.
   * From the viewpoint of source code, these methods can take any arguments
   * and their result can be cast to any return type.
   * Formally this is accomplished by giving the invoker methods
   * {@code Object} return types and variable arity {@code Object} arguments,
   * but they have an additional quality called <em>signature polymorphism</em>
   * which connects this freedom of invocation directly to the JVM execution stack.
   * <p>
   * As is usual with virtual methods, source-level calls to {@code invokeExact}
   * and {@code invoke} compile to an {@code invokevirtual} instruction.
   * More unusually, the compiler must record the actual argument types,
   * and may not perform method invocation conversions on the arguments.
   * Instead, it must push them on the stack according to their own unconverted types.
   * The method handle object itself is pushed on the stack before the arguments.
   * The compiler then calls the method handle with a symbolic type descriptor which
   * describes the argument and return types.
   * <p>
   * To issue a complete symbolic type descriptor, the compiler must also determine
   * the return type.  This is based on a cast on the method invocation expression,
   * if there is one, or else {@code Object} if the invocation is an expression
   * or else {@code void} if the invocation is a statement.
   * The cast may be to a primitive type (but not {@code void}).
   * <p>
   * As a corner case, an uncasted {@code null} argument is given
   * a symbolic type descriptor of {@code java.lang.Void}.
   * The ambiguity with the type {@code Void} is harmless, since there are no references of type
   * {@code Void} except the null reference.
   *
   * <h1>Method handle invocation</h1>
   * The first time a {@code invokevirtual} instruction is executed
   * it is linked, by symbolically resolving the names in the instruction
   * and verifying that the method call is statically legal.
   * This is true of calls to {@code invokeExact} and {@code invoke}.
   * In this case, the symbolic type descriptor emitted by the compiler is checked for
   * correct syntax and names it contains are resolved.
   * Thus, an {@code invokevirtual} instruction which invokes
   * a method handle will always link, as long
   * as the symbolic type descriptor is syntactically well-formed
   * and the types exist.
   * <p>
   * When the {@code invokevirtual} is executed after linking,
   * the receiving method handle's type is first checked by the JVM
   * to ensure that it matches the symbolic type descriptor.
   * If the type match fails, it means that the method which the
   * caller is invoking is not present on the individual
   * method handle being invoked.
   * <p>
   * In the case of {@code invokeExact}, the type descriptor of the invocation
   * (after resolving symbolic type names) must exactly match the method type
   * of the receiving method handle.
   * In the case of plain, inexact {@code invoke}, the resolved type descriptor
   * must be a valid argument to the receiver's {@link #asType asType} method.
   * Thus, plain {@code invoke} is more permissive than {@code invokeExact}.
   * <p>
   * After type matching, a call to {@code invokeExact} directly
   * and immediately invoke the method handle's underlying method
   * (or other behavior, as the case may be).
   * <p>
   * A call to plain {@code invoke} works the same as a call to
   * {@code invokeExact}, if the symbolic type descriptor specified by the caller
   * exactly matches the method handle's own type.
   * If there is a type mismatch, {@code invoke} attempts
   * to adjust the type of the receiving method handle,
   * as if by a call to {@link #asType asType},
   * to obtain an exactly invokable method handle {@code M2}.
   * This allows a more powerful negotiation of method type
   * between caller and callee.
   * <p>
   * (<em>Note:</em> The adjusted method handle {@code M2} is not directly observable,
   * and implementations are therefore not required to materialize it.)
   *
   * <h1>Invocation checking</h1>
   * In typical programs, method handle type matching will usually succeed.
   * But if a match fails, the JVM will throw a {@link WrongMethodTypeException},
   * either directly (in the case of {@code invokeExact}) or indirectly as if
   * by a failed call to {@code asType} (in the case of {@code invoke}).
   * <p>
   * Thus, a method type mismatch which might show up as a linkage error
   * in a statically typed program can show up as
   * a dynamic {@code WrongMethodTypeException}
   * in a program which uses method handles.
   * <p>
   * Because method types contain "live" {@code Class} objects,
   * method type matching takes into account both types names and class loaders.
   * Thus, even if a method handle {@code M} is created in one
   * class loader {@code L1} and used in another {@code L2},
   * method handle calls are type-safe, because the caller's symbolic type
   * descriptor, as resolved in {@code L2},
   * is matched against the original callee method's symbolic type descriptor,
   * as resolved in {@code L1}.
   * The resolution in {@code L1} happens when {@code M} is created
   * and its type is assigned, while the resolution in {@code L2} happens
   * when the {@code invokevirtual} instruction is linked.
   * <p>
   * Apart from the checking of type descriptors,
   * a method handle's capability to call its underlying method is unrestricted.
   * If a method handle is formed on a non-public method by a class
   * that has access to that method, the resulting handle can be used
   * in any place by any caller who receives a reference to it.
   * <p>
   * Unlike with the Core Reflection API, where access is checked every time
   * a reflective method is invoked,
   * method handle access checking is performed
   * <a href="MethodHandles.Lookup.html#access">when the method handle is created</a>.
   * In the case of {@code ldc} (see below), access checking is performed as part of linking
   * the constant pool entry underlying the constant method handle.
   * <p>
   * Thus, handles to non-public methods, or to methods in non-public classes,
   * should generally be kept secret.
   * They should not be passed to untrusted code unless their use from
   * the untrusted code would be harmless.
   *
   * <h1>Method handle creation</h1>
   * Java code can create a method handle that directly accesses
   * any method, constructor, or field that is accessible to that code.
   * This is done via a reflective, capability-based API called
   * {@link MethodHandles.Lookup MethodHandles.Lookup}
   * For example, a static method handle can be obtained
   * from {@link MethodHandles.Lookup#findStatic Lookup.findStatic}.
   * There are also conversion methods from Core Reflection API objects,
   * such as {@link MethodHandles.Lookup#unreflect Lookup.unreflect}.
   * <p>
   * Like classes and strings, method handles that correspond to accessible
   * fields, methods, and constructors can also be represented directly
   * in a class file's constant pool as constants to be loaded by {@code ldc} bytecodes.
   * A new type of constant pool entry, {@code CONSTANT_MethodHandle},
   * refers directly to an associated {@code CONSTANT_Methodref},
   * {@code CONSTANT_InterfaceMethodref}, or {@code CONSTANT_Fieldref}
   * constant pool entry.
   * (For full details on method handle constants,
   * see sections 4.4.8 and 5.4.3.5 of the Java Virtual Machine Specification.)
   * <p>
   * Method handles produced by lookups or constant loads from methods or
   * constructors with the variable arity modifier bit ({@code 0x0080})
   * have a corresponding variable arity, as if they were defined with
   * the help of {@link #asVarargsCollector asVarargsCollector}.
   * <p>
   * A method reference may refer either to a static or non-static method.
   * In the non-static case, the method handle type includes an explicit
   * receiver argument, prepended before any other arguments.
   * In the method handle's type, the initial receiver argument is typed
   * according to the class under which the method was initially requested.
   * (E.g., if a non-static method handle is obtained via {@code ldc},
   * the type of the receiver is the class named in the constant pool entry.)
   * <p>
   * Method handle constants are subject to the same link-time access checks
   * their corresponding bytecode instructions, and the {@code ldc} instruction
   * will throw corresponding linkage errors if the bytecode behaviors would
   * throw such errors.
   * <p>
   * As a corollary of this, access to protected members is restricted
   * to receivers only of the accessing class, or one of its subclasses,
   * and the accessing class must in turn be a subclass (or package sibling)
   * of the protected member's defining class.
   * If a method reference refers to a protected non-static method or field
   * of a class outside the current package, the receiver argument will
   * be narrowed to the type of the accessing class.
   * <p>
   * When a method handle to a virtual method is invoked, the method is
   * always looked up in the receiver (that is, the first argument).
   * <p>
   * A non-virtual method handle to a specific virtual method implementation
   * can also be created.  These do not perform virtual lookup based on
   * receiver type.  Such a method handle simulates the effect of
   * an {@code invokespecial} instruction to the same method.
   *
   * <h1>Usage examples</h1>
   * Here are some examples of usage:
   * <blockquote><pre>{@code
  Object x, y; String s; int i;
  MethodType mt; MethodHandle mh;
  MethodHandles.Lookup lookup = MethodHandles.lookup();
  // mt is (char,char)String
  mt = MethodType.methodType(String.class, char.class, char.class);
  mh = lookup.findVirtual(String.class, "replace", mt);
  s = (String) mh.invokeExact("daddy",'d','n');
  // invokeExact(Ljava/lang/String;CC)Ljava/lang/String;
  assertEquals(s, "nanny");
  // weakly typed invocation (using MHs.invoke)
  s = (String) mh.invokeWithArguments("sappy", 'p', 'v');
  assertEquals(s, "savvy");
  // mt is (Object[])List
  mt = MethodType.methodType(java.util.List.class, Object[].class);
  mh = lookup.findStatic(java.util.Arrays.class, "asList", mt);
  assert(mh.isVarargsCollector());
  x = mh.invoke("one", "two");
  // invoke(Ljava/lang/String;Ljava/lang/String;)Ljava/lang/Object;
  assertEquals(x, java.util.Arrays.asList("one","two"));
  // mt is (Object,Object,Object)Object
  mt = MethodType.genericMethodType(3);
  mh = mh.asType(mt);
  x = mh.invokeExact((Object)1, (Object)2, (Object)3);
  // invokeExact(Ljava/lang/Object;Ljava/lang/Object;Ljava/lang/Object;)Ljava/lang/Object;
  assertEquals(x, java.util.Arrays.asList(1,2,3));
  // mt is ()int
  mt = MethodType.methodType(int.class);
  mh = lookup.findVirtual(java.util.List.class, "size", mt);
  i = (int) mh.invokeExact(java.util.Arrays.asList(1,2,3));
  // invokeExact(Ljava/util/List;)I
  assert(i == 3);
  mt = MethodType.methodType(void.class, String.class);
  mh = lookup.findVirtual(java.io.PrintStream.class, "println", mt);
  mh.invokeExact(System.out, "Hello, world.");
  // invokeExact(Ljava/io/PrintStream;Ljava/lang/String;)V
   * }</pre></blockquote>
   * Each of the above calls to {@code invokeExact} or plain {@code invoke}
   * generates a single invokevirtual instruction with
   * the symbolic type descriptor indicated in the following comment.
   * In these examples, the helper method {@code assertEquals} is assumed to
   * be a method which calls {@link java.util.Objects#equals(Object,Object) Objects.equals}
   * on its arguments, and asserts that the result is true.
   *
   * <h1>Exceptions</h1>
   * The methods {@code invokeExact} and {@code invoke} are declared
   * to throw {@link Throwable Throwable},
   * which is to say that there is no static restriction on what a method handle
   * can throw.  Since the JVM does not distinguish between checked
   * and unchecked exceptions (other than by their class, of course),
   * there is no particular effect on bytecode shape from ascribing
   * checked exceptions to method handle invocations.  But in Java source
   * code, methods which perform method handle calls must either explicitly
   * throw {@code Throwable}, or else must catch all
   * throwables locally, rethrowing only those which are legal in the context,
   * and wrapping ones which are illegal.
   *
   * <h1><a name="sigpoly"></a>Signature polymorphism</h1>
   * The unusual compilation and linkage behavior of
   * {@code invokeExact} and plain {@code invoke}
   * is referenced by the term <em>signature polymorphism</em>.
   * As defined in the Java Language Specification,
   * a signature polymorphic method is one which can operate with
   * any of a wide range of call signatures and return types.
   * <p>
   * In source code, a call to a signature polymorphic method will
   * compile, regardless of the requested symbolic type descriptor.
   * As usual, the Java compiler emits an {@code invokevirtual}
   * instruction with the given symbolic type descriptor against the named method.
   * The unusual part is that the symbolic type descriptor is derived from
   * the actual argument and return types, not from the method declaration.
   * <p>
   * When the JVM processes bytecode containing signature polymorphic calls,
   * it will successfully link any such call, regardless of its symbolic type descriptor.
   * (In order to retain type safety, the JVM will guard such calls with suitable
   * dynamic type checks, as described elsewhere.)
   * <p>
   * Bytecode generators, including the compiler back end, are required to emit
   * untransformed symbolic type descriptors for these methods.
   * Tools which determine symbolic linkage are required to accept such
   * untransformed descriptors, without reporting linkage errors.
   *
   * <h1>Interoperation between method handles and the Core Reflection API</h1>
   * Using factory methods in the {@link MethodHandles.Lookup Lookup} API,
   * any class member represented by a Core Reflection API object
   * can be converted to a behaviorally equivalent method handle.
   * For example, a reflective {@link java.lang.reflect.Method Method} can
   * be converted to a method handle using
   * {@link MethodHandles.Lookup#unreflect Lookup.unreflect}.
   * The resulting method handles generally provide more direct and efficient
   * access to the underlying class members.
   * <p>
   * As a special case,
   * when the Core Reflection API is used to view the signature polymorphic
   * methods {@code invokeExact} or plain {@code invoke} in this class,
   * they appear as ordinary non-polymorphic methods.
   * Their reflective appearance, as viewed by
   * {@link Class#getDeclaredMethod Class.getDeclaredMethod},
   * is unaffected by their special status in this API.
   * For example, {@link java.lang.reflect.Method#getModifiers Method.getModifiers}
   * will report exactly those modifier bits required for any similarly
   * declared method, including in this case {@code native} and {@code varargs} bits.
   * <p>
   * As with any reflected method, these methods (when reflected) may be
   * invoked via {@link java.lang.reflect.Method#invoke java.lang.reflect.Method.invoke}.
   * However, such reflective calls do not result in method handle invocations.
   * Such a call, if passed the required argument
   * (a single one, of type {@code Object[]}), will ignore the argument and
   * will throw an {@code UnsupportedOperationException}.
   * <p>
   * Since {@code invokevirtual} instructions can natively
   * invoke method handles under any symbolic type descriptor, this reflective view conflicts
   * with the normal presentation of these methods via bytecodes.
   * Thus, these two native methods, when reflectively viewed by
   * {@code Class.getDeclaredMethod}, may be regarded as placeholders only.
   * <p>
   * In order to obtain an invoker method for a particular type descriptor,
   * use {@link MethodHandles#exactInvoker MethodHandles.exactInvoker},
   * or {@link MethodHandles#invoker MethodHandles.invoker}.
   * The {@link MethodHandles.Lookup#findVirtual Lookup.findVirtual}
   * API is also able to return a method handle
   * to call {@code invokeExact} or plain {@code invoke},
   * for any specified type descriptor .
   *
   * <h1>Interoperation between method handles and Java generics</h1>
   * A method handle can be obtained on a method, constructor, or field
   * which is declared with Java generic types.
   * As with the Core Reflection API, the type of the method handle
   * will constructed from the erasure of the source-level type.
   * When a method handle is invoked, the types of its arguments
   * or the return value cast type may be generic types or type instances.
   * If this occurs, the compiler will replace those
   * types by their erasures when it constructs the symbolic type descriptor
   * for the {@code invokevirtual} instruction.
   * <p>
   * Method handles do not represent
   * their function-like types in terms of Java parameterized (generic) types,
   * because there are three mismatches between function-like types and parameterized
   * Java types.
   * <ul>
   * <li>Method types range over all possible arities,
   * from no arguments to up to the  <a href="MethodHandle.html#maxarity">maximum number</a> of allowed arguments.
   * Generics are not variadic, and so cannot represent this.</li>
   * <li>Method types can specify arguments of primitive types,
   * which Java generic types cannot range over.</li>
   * <li>Higher order functions over method handles (combinators) are
   * often generic across a wide range of function types, including
   * those of multiple arities.  It is impossible to represent such
   * genericity with a Java type parameter.</li>
   * </ul>
   *
   * <h1><a name="maxarity"></a>Arity limits</h1>
   * The JVM imposes on all methods and constructors of any kind an absolute
   * limit of 255 stacked arguments.  This limit can appear more restrictive
   * in certain cases:
   * <ul>
   * <li>A {@code long} or {@code double} argument counts (for purposes of arity limits) as two argument slots.
   * <li>A non-static method consumes an extra argument for the object on which the method is called.
   * <li>A constructor consumes an extra argument for the object which is being constructed.
   * <li>Since a method handle&rsquo;s {@code invoke} method (or other signature-polymorphic method) is non-virtual,
   *     it consumes an extra argument for the method handle itself, in addition to any non-virtual receiver object.
   * </ul>
   * These limits imply that certain method handles cannot be created, solely because of the JVM limit on stacked arguments.
   * For example, if a static JVM method accepts exactly 255 arguments, a method handle cannot be created for it.
   * Attempts to create method handles with impossible method types lead to an {@link IllegalArgumentException}.
   * In particular, a method handle&rsquo;s type must not have an arity of the exact maximum 255.
   *
   * @see MethodType
   * @see MethodHandles
   * @author John Rose, JSR 292 EG
   */
  public abstract class MethodHandle {
      // Android-removed: MethodHandleImpl.initStatics() unused on Android.
      // static { MethodHandleImpl.initStatics(); }
  
      /**
       * Internal marker interface which distinguishes (to the Java compiler)
       * those methods which are <a href="MethodHandle.html#sigpoly">signature polymorphic</a>.
       *
       * @hide
       */
      @java.lang.annotation.Target({java.lang.annotation.ElementType.METHOD})
      @java.lang.annotation.Retention(java.lang.annotation.RetentionPolicy.RUNTIME)
      // Android-changed: Made public @hide as otherwise it breaks the stubs generation.
      // @interface PolymorphicSignature { }
      public @interface PolymorphicSignature { }
  
      // Android-added: Comment to differentiate between type and nominalType.
      /**
       * The type of this method handle, this corresponds to the exact type of the method
       * being invoked.
       *
       * @see #nominalType
       */
      private final MethodType type;
      // Android-removed: LambdaForm and customizationCount unused on Android.
      // They will be substituted with appropriate implementation / delegate classes.
      /*
      /*private* final LambdaForm form;
      // form is not private so that invokers can easily fetch it
      /*private* MethodHandle asTypeCache;
      // asTypeCache is not private so that invokers can easily fetch it
      /*non-public* byte customizationCount;
      // customizationCount should be accessible from invokers
      */
  
      // BEGIN Android-added: Android specific implementation.
      // The MethodHandle functionality is tightly coupled with internal details of the runtime and
      // so Android has a completely different implementation compared to the RI.
      /**
       * The nominal type of this method handle, will be non-null if a method handle declares
       * a different type from its "real" type, which is either the type of the method being invoked
       * or the type of the emulated stackframe expected by an underyling adapter.
       */
      private MethodType nominalType;
  
      /**
       * The spread invoker associated with this type with zero trailing arguments.
       * This is used to speed up invokeWithArguments.
       */
      private MethodHandle cachedSpreadInvoker;
  
      /**
       * The INVOKE* constants and SGET/SPUT and IGET/IPUT constants specify the behaviour of this
       * method handle with respect to the ArtField* or the ArtMethod* that it operates on. These
       * behaviours are equivalent to the dex bytecode behaviour on the respective method_id or
       * field_id in the equivalent instruction.
       *
       * INVOKE_TRANSFORM is a special type of handle which doesn't encode any dex bytecode behaviour,
       * instead it transforms the list of input arguments or performs other higher order operations
       * before (optionally) delegating to another method handle.
       *
       * INVOKE_CALLSITE_TRANSFORM is a variation on INVOKE_TRANSFORM where the method type of
       * a MethodHandle dynamically varies based on the callsite. This is used by
       * the VarargsCollector implementation which places any number of trailing arguments
       * into an array before invoking an arity method. The "any number of trailing arguments" means
       * it would otherwise generate WrongMethodTypeExceptions as the callsite method type and
       * VarargsCollector method type appear incompatible.
       */
  
      /** @hide */ public static final int INVOKE_VIRTUAL = 0;
      /** @hide */ public static final int INVOKE_SUPER = 1;
      /** @hide */ public static final int INVOKE_DIRECT = 2;
      /** @hide */ public static final int INVOKE_STATIC = 3;
      /** @hide */ public static final int INVOKE_INTERFACE = 4;
      /** @hide */ public static final int INVOKE_TRANSFORM = 5;
      /** @hide */ public static final int INVOKE_CALLSITE_TRANSFORM = 6;
      /** @hide */ public static final int INVOKE_VAR_HANDLE = 7;
      /** @hide */ public static final int INVOKE_VAR_HANDLE_EXACT = 8;
      /** @hide */ public static final int IGET = 9;
      /** @hide */ public static final int IPUT = 10;
      /** @hide */ public static final int SGET = 11;
      /** @hide */ public static final int SPUT = 12;
  
      // The kind of this method handle (used by the runtime). This is one of the INVOKE_*
      // constants or SGET/SPUT, IGET/IPUT.
      /** @hide */ protected final int handleKind;
  
      // The ArtMethod* or ArtField* associated with this method handle (used by the runtime).
      /** @hide */ protected final long artFieldOrMethod;
  
      /** @hide */
      protected MethodHandle(long artFieldOrMethod, int handleKind, MethodType type) {
          this.artFieldOrMethod = artFieldOrMethod;
          this.handleKind = handleKind;
          this.type = type;
      }
      // END Android-added: Android specific implementation.
  
      /**
       * Reports the type of this method handle.
       * Every invocation of this method handle via {@code invokeExact} must exactly match this type.
       * @return the method handle type
       */
      public MethodType type() {
          // Android-added: Added nominalType field.
          if (nominalType != null) {
              return nominalType;
          }
  
          return type;
      }
  
      // BEGIN Android-removed: LambdaForm unsupported on Android.
      /*
      /**
       * Package-private constructor for the method handle implementation hierarchy.
       * Method handle inheritance will be contained completely within
       * the {@code java.lang.invoke} package.
       *
      // @param type type (permanently assigned) of the new method handle
      /*non-public* MethodHandle(MethodType type, LambdaForm form) {
          type.getClass();  // explicit NPE
          form.getClass();  // explicit NPE
          this.type = type;
          this.form = form.uncustomize();
  
          this.form.prepare();  // TO DO:  Try to delay this step until just before invocation.
      }
      */
      // END Android-removed: LambdaForm unsupported on Android.
  
      /**
       * Invokes the method handle, allowing any caller type descriptor, but requiring an exact type match.
       * The symbolic type descriptor at the call site of {@code invokeExact} must
       * exactly match this method handle's {@link #type type}.
       * No conversions are allowed on arguments or return values.
       * <p>
       * When this method is observed via the Core Reflection API,
       * it will appear as a single native method, taking an object array and returning an object.
       * If this native method is invoked directly via
       * {@link java.lang.reflect.Method#invoke java.lang.reflect.Method.invoke}, via JNI,
       * or indirectly via {@link MethodHandles.Lookup#unreflect Lookup.unreflect},
       * it will throw an {@code UnsupportedOperationException}.
       * @param args the signature-polymorphic parameter list, statically represented using varargs
       * @return the signature-polymorphic result, statically represented using {@code Object}
       * @throws WrongMethodTypeException if the target's type is not identical with the caller's symbolic type descriptor
       * @throws Throwable anything thrown by the underlying method propagates unchanged through the method handle call
       */
      public final native @PolymorphicSignature Object invokeExact(Object... args) throws Throwable;
  
      /**
       * Invokes the method handle, allowing any caller type descriptor,
       * and optionally performing conversions on arguments and return values.
       * <p>
       * If the call site's symbolic type descriptor exactly matches this method handle's {@link #type type},
       * the call proceeds as if by {@link #invokeExact invokeExact}.
       * <p>
       * Otherwise, the call proceeds as if this method handle were first
       * adjusted by calling {@link #asType asType} to adjust this method handle
       * to the required type, and then the call proceeds as if by
       * {@link #invokeExact invokeExact} on the adjusted method handle.
       * <p>
       * There is no guarantee that the {@code asType} call is actually made.
       * If the JVM can predict the results of making the call, it may perform
       * adaptations directly on the caller's arguments,
       * and call the target method handle according to its own exact type.
       * <p>
       * The resolved type descriptor at the call site of {@code invoke} must
       * be a valid argument to the receivers {@code asType} method.
       * In particular, the caller must specify the same argument arity
       * as the callee's type,
       * if the callee is not a {@linkplain #asVarargsCollector variable arity collector}.
       * <p>
       * When this method is observed via the Core Reflection API,
       * it will appear as a single native method, taking an object array and returning an object.
       * If this native method is invoked directly via
       * {@link java.lang.reflect.Method#invoke java.lang.reflect.Method.invoke}, via JNI,
       * or indirectly via {@link MethodHandles.Lookup#unreflect Lookup.unreflect},
       * it will throw an {@code UnsupportedOperationException}.
       * @param args the signature-polymorphic parameter list, statically represented using varargs
       * @return the signature-polymorphic result, statically represented using {@code Object}
       * @throws WrongMethodTypeException if the target's type cannot be adjusted to the caller's symbolic type descriptor
       * @throws ClassCastException if the target's type can be adjusted to the caller, but a reference cast fails
       * @throws Throwable anything thrown by the underlying method propagates unchanged through the method handle call
       */
      public final native @PolymorphicSignature Object invoke(Object... args) throws Throwable;
  
      // BEGIN Android-removed: RI implementation unused on Android.
      /*
      /**
       * Private method for trusted invocation of a method handle respecting simplified signatures.
       * Type mismatches will not throw {@code WrongMethodTypeException}, but could crash the JVM.
       * <p>
       * The caller signature is restricted to the following basic types:
       * Object, int, long, float, double, and void return.
       * <p>
       * The caller is responsible for maintaining type correctness by ensuring
       * that the each outgoing argument value is a member of the range of the corresponding
       * callee argument type.
       * (The caller should therefore issue appropriate casts and integer narrowing
       * operations on outgoing argument values.)
       * The caller can assume that the incoming result value is part of the range
       * of the callee's return type.
       * @param args the signature-polymorphic parameter list, statically represented using varargs
       * @return the signature-polymorphic result, statically represented using {@code Object}
       *
      /*non-public* final native @PolymorphicSignature Object invokeBasic(Object... args) throws Throwable;
  
      /**
       * Private method for trusted invocation of a MemberName of kind {@code REF_invokeVirtual}.
       * The caller signature is restricted to basic types as with {@code invokeBasic}.
       * The trailing (not leading) argument must be a MemberName.
       * @param args the signature-polymorphic parameter list, statically represented using varargs
       * @return the signature-polymorphic result, statically represented using {@code Object}
       *
      /*non-public* static native @PolymorphicSignature Object linkToVirtual(Object... args) throws Throwable;
  
      /**
       * Private method for trusted invocation of a MemberName of kind {@code REF_invokeStatic}.
       * The caller signature is restricted to basic types as with {@code invokeBasic}.
       * The trailing (not leading) argument must be a MemberName.
       * @param args the signature-polymorphic parameter list, statically represented using varargs
       * @return the signature-polymorphic result, statically represented using {@code Object}
       *
      /*non-public* static native @PolymorphicSignature Object linkToStatic(Object... args) throws Throwable;
  
      /**
       * Private method for trusted invocation of a MemberName of kind {@code REF_invokeSpecial}.
       * The caller signature is restricted to basic types as with {@code invokeBasic}.
       * The trailing (not leading) argument must be a MemberName.
       * @param args the signature-polymorphic parameter list, statically represented using varargs
       * @return the signature-polymorphic result, statically represented using {@code Object}
       *
      /*non-public* static native @PolymorphicSignature Object linkToSpecial(Object... args) throws Throwable;
  
      /**
       * Private method for trusted invocation of a MemberName of kind {@code REF_invokeInterface}.
       * The caller signature is restricted to basic types as with {@code invokeBasic}.
       * The trailing (not leading) argument must be a MemberName.
       * @param args the signature-polymorphic parameter list, statically represented using varargs
       * @return the signature-polymorphic result, statically represented using {@code Object}
       *
      /*non-public* static native @PolymorphicSignature Object linkToInterface(Object... args) throws Throwable;
      */
      // END Android-removed: RI implementation unused on Android.
  
      /**
       * Performs a variable arity invocation, passing the arguments in the given list
       * to the method handle, as if via an inexact {@link #invoke invoke} from a call site
       * which mentions only the type {@code Object}, and whose arity is the length
       * of the argument list.
       * <p>
       * Specifically, execution proceeds as if by the following steps,
       * although the methods are not guaranteed to be called if the JVM
       * can predict their effects.
       * <ul>
       * <li>Determine the length of the argument array as {@code N}.
       *     For a null reference, {@code N=0}. </li>
       * <li>Determine the general type {@code TN} of {@code N} arguments as
       *     as {@code TN=MethodType.genericMethodType(N)}.</li>
       * <li>Force the original target method handle {@code MH0} to the
       *     required type, as {@code MH1 = MH0.asType(TN)}. </li>
       * <li>Spread the array into {@code N} separate arguments {@code A0, ...}. </li>
       * <li>Invoke the type-adjusted method handle on the unpacked arguments:
       *     MH1.invokeExact(A0, ...). </li>
       * <li>Take the return value as an {@code Object} reference. </li>
       * </ul>
       * <p>
       * Because of the action of the {@code asType} step, the following argument
       * conversions are applied as necessary:
       * <ul>
       * <li>reference casting
       * <li>unboxing
       * <li>widening primitive conversions
       * </ul>
       * <p>
       * The result returned by the call is boxed if it is a primitive,
       * or forced to null if the return type is void.
       * <p>
       * This call is equivalent to the following code:
       * <blockquote><pre>{@code
       * MethodHandle invoker = MethodHandles.spreadInvoker(this.type(), 0);
       * Object result = invoker.invokeExact(this, arguments);
       * }</pre></blockquote>
       * <p>
       * Unlike the signature polymorphic methods {@code invokeExact} and {@code invoke},
       * {@code invokeWithArguments} can be accessed normally via the Core Reflection API and JNI.
       * It can therefore be used as a bridge between native or reflective code and method handles.
       *
       * @param arguments the arguments to pass to the target
       * @return the result returned by the target
       * @throws ClassCastException if an argument cannot be converted by reference casting
       * @throws WrongMethodTypeException if the target's type cannot be adjusted to take the given number of {@code Object} arguments
       * @throws Throwable anything thrown by the target method invocation
       * @see MethodHandles#spreadInvoker
       */
      public Object invokeWithArguments(Object... arguments) throws Throwable {
          // BEGIN Android-changed: Android specific implementation.
          // MethodType invocationType = MethodType.genericMethodType(arguments == null ? 0 : arguments.length);
          // return invocationType.invokers().spreadInvoker(0).invokeExact(asType(invocationType), arguments);
          MethodHandle invoker = null;
          synchronized (this) {
              if (cachedSpreadInvoker == null) {
                  cachedSpreadInvoker = MethodHandles.spreadInvoker(this.type(), 0);
              }
  
              invoker = cachedSpreadInvoker;
          }
  
          return invoker.invoke(this, arguments);
          // END Android-changed: Android specific implementation.
      }
  
      /**
       * Performs a variable arity invocation, passing the arguments in the given array
       * to the method handle, as if via an inexact {@link #invoke invoke} from a call site
       * which mentions only the type {@code Object}, and whose arity is the length
       * of the argument array.
       * <p>
       * This method is also equivalent to the following code:
       * <blockquote><pre>{@code
       *   invokeWithArguments(arguments.toArray()
       * }</pre></blockquote>
       *
       * @param arguments the arguments to pass to the target
       * @return the result returned by the target
       * @throws NullPointerException if {@code arguments} is a null reference
       * @throws ClassCastException if an argument cannot be converted by reference casting
       * @throws WrongMethodTypeException if the target's type cannot be adjusted to take the given number of {@code Object} arguments
       * @throws Throwable anything thrown by the target method invocation
       */
      public Object invokeWithArguments(java.util.List<?> arguments) throws Throwable {
          return invokeWithArguments(arguments.toArray());
      }
  
      /**
       * Produces an adapter method handle which adapts the type of the
       * current method handle to a new type.
       * 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 {@code this}.
       * <p>
       * The new method handle, when invoked, will perform the following
       * steps:
       * <ul>
       * <li>Convert the incoming argument list to match the original
       *     method handle's argument list.
       * <li>Invoke the original method handle on the converted argument list.
       * <li>Convert any result returned by the original method handle
       *     to the return type of new method handle.
       * </ul>
       * <p>
       * This method provides the crucial behavioral difference between
       * {@link #invokeExact invokeExact} and plain, inexact {@link #invoke invoke}.
       * The two methods
       * perform the same steps when the caller's type descriptor exactly m atches
       * the callee's, but when the types differ, plain {@link #invoke invoke}
       * also calls {@code asType} (or some internal equivalent) in order
       * to match up the caller's and callee's types.
       * <p>
       * If the current method is a variable arity method handle
       * argument list conversion may involve the conversion and collection
       * of several arguments into an array, as
       * {@linkplain #asVarargsCollector described elsewhere}.
       * In every other case, all conversions are applied <em>pairwise</em>,
       * which means that each argument or return value is converted to
       * exactly one argument or return value (or no return value).
       * The applied conversions are defined by consulting the
       * the corresponding component types of the old and new
       * method handle types.
       * <p>
       * Let <em>T0</em> and <em>T1</em> be corresponding new and old parameter types,
       * or old and new return types.  Specifically, for some valid index {@code i}, let
       * <em>T0</em>{@code =newType.parameterType(i)} and <em>T1</em>{@code =this.type().parameterType(i)}.
       * Or else, going the other way for return values, let
       * <em>T0</em>{@code =this.type().returnType()} and <em>T1</em>{@code =newType.returnType()}.
       * If the types are the same, the new method handle makes no change
       * to the corresponding argument or return value (if any).
       * Otherwise, one of the following conversions is applied
       * if possible:
       * <ul>
       * <li>If <em>T0</em> and <em>T1</em> are references, then a cast to <em>T1</em> is applied.
       *     (The types do not need to be related in any particular way.
       *     This is because a dynamic value of null can convert to any reference type.)
       * <li>If <em>T0</em> and <em>T1</em> are primitives, then a Java method invocation
       *     conversion (JLS 5.3) is applied, if one exists.
       *     (Specifically, <em>T0</em> must convert to <em>T1</em> by a widening primitive conversion.)
       * <li>If <em>T0</em> is a primitive and <em>T1</em> a reference,
       *     a Java casting conversion (JLS 5.5) is applied if one exists.
       *     (Specifically, the value is boxed from <em>T0</em> to its wrapper class,
       *     which is then widened as needed to <em>T1</em>.)
       * <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 method invocation conversion (JLS 5.3)
       *     on the primitive value.  (These are the primitive widening conversions.)
       *     <em>T0</em> must be a wrapper class or a supertype of one.
       *     (In the case where <em>T0</em> is Object, these are the conversions
       *     allowed by {@link java.lang.reflect.Method#invoke java.lang.reflect.Method.invoke}.)
       *     The unboxing conversion must have a possibility of success, which means that
       *     if <em>T0</em> is not itself a wrapper class, there must exist at least one
       *     wrapper class <em>TW</em> which is a subtype of <em>T0</em> and whose unboxed
       *     primitive value can be widened to <em>T1</em>.
       * <li>If the return type <em>T1</em> is marked as void, any returned value is discarded
       * <li>If the return type <em>T0</em> is void and <em>T1</em> a reference, a null value is introduced.
       * <li>If the return type <em>T0</em> is void and <em>T1</em> a primitive,
       *     a zero value is introduced.
       * </ul>
       * (<em>Note:</em> Both <em>T0</em> and <em>T1</em> may be regarded as static types,
       * because neither corresponds specifically to the <em>dynamic type</em> of any
       * actual argument or return value.)
       * <p>
       * The method handle conversion cannot be made if any one of the required
       * pairwise conversions cannot be made.
       * <p>
       * At runtime, the conversions applied to reference arguments
       * or return values may require additional runtime checks which can fail.
       * An unboxing operation may fail because the original reference is null,
       * causing a {@link NullPointerException NullPointerException}.
       * An unboxing operation or a reference cast may also fail on a reference
       * to an object of the wrong type,
       * causing a {@link ClassCastException ClassCastException}.
       * Although an unboxing operation may accept several kinds of wrappers,
       * if none are available, a {@code ClassCastException} will be thrown.
       *
       * @param newType the expected type of the new method handle
       * @return a method handle which delegates to {@code this} after performing
       *           any necessary argument conversions, and arranges for any
       *           necessary return value conversions
       * @throws NullPointerException if {@code newType} is a null reference
       * @throws WrongMethodTypeException if the conversion cannot be made
       * @see MethodHandles#explicitCastArguments
       */
      public MethodHandle asType(MethodType newType) {
          // Fast path alternative to a heavyweight {@code asType} call.
          // Return 'this' if the conversion will be a no-op.
          if (newType == type) {
              return this;
          }
          // Android-removed: Type conversion memoizing is unsupported on Android.
          /*
          // Return 'this.asTypeCache' if the conversion is already memoized.
          MethodHandle atc = asTypeCached(newType);
          if (atc != null) {
              return atc;
          }
          */
          return asTypeUncached(newType);
      }
  
      // Android-removed: Type conversion memoizing is unsupported on Android.
      /*
      private MethodHandle asTypeCached(MethodType newType) {
          MethodHandle atc = asTypeCache;
          if (atc != null && newType == atc.type) {
              return atc;
          }
          return null;
      }
      */
  
      /** Override this to change asType behavior. */
      /*non-public*/ MethodHandle asTypeUncached(MethodType newType) {
          if (!type.isConvertibleTo(newType))
              throw new WrongMethodTypeException("cannot convert "+this+" to "+newType);
          // BEGIN Android-changed: Android specific implementation.
          // return asTypeCache = MethodHandleImpl.makePairwiseConvert(this, newType, true);
          MethodHandle mh = duplicate();
          mh.nominalType = newType;
          return mh;
          // END Android-changed: Android specific implementation.
      }
  
      /**
       * Makes an <em>array-spreading</em> method handle, which accepts a trailing array argument
       * and spreads its elements as positional arguments.
       * The new method handle adapts, as its <i>target</i>,
       * the current method handle.  The type of the adapter will be
       * the same as the type of the target, except that the final
       * {@code arrayLength} parameters of the target's type are replaced
       * by a single array parameter of type {@code arrayType}.
       * <p>
       * If the array element type differs from any of the corresponding
       * argument types on the original target,
       * the original target is adapted to take the array elements directly,
       * as if by a call to {@link #asType asType}.
       * <p>
       * When called, the adapter replaces a trailing array argument
       * by the array's elements, each as its own argument to the target.
       * (The order of the arguments is preserved.)
       * They are converted pairwise by casting and/or unboxing
       * to the types of the trailing parameters of the target.
       * Finally the target is called.
       * What the target eventually returns is returned unchanged by the adapter.
       * <p>
       * Before calling the target, the adapter verifies that the array
       * contains exactly enough elements to provide a correct argument count
       * to the target method handle.
       * (The array may also be null when zero elements are required.)
       * <p>
       * If, when the adapter is called, the supplied array argument does
       * not have the correct number of elements, the adapter will throw
       * an {@link IllegalArgumentException} instead of invoking the target.
       * <p>
       * Here are some simple examples of array-spreading method handles:
       * <blockquote><pre>{@code
  MethodHandle equals = publicLookup()
    .findVirtual(String.class, "equals", methodType(boolean.class, Object.class));
  assert( (boolean) equals.invokeExact("me", (Object)"me"));
  assert(!(boolean) equals.invokeExact("me", (Object)"thee"));
  // spread both arguments from a 2-array:
  MethodHandle eq2 = equals.asSpreader(Object[].class, 2);
  assert( (boolean) eq2.invokeExact(new Object[]{ "me", "me" }));
  assert(!(boolean) eq2.invokeExact(new Object[]{ "me", "thee" }));
  // try to spread from anything but a 2-array:
  for (int n = 0; n <= 10; n++) {
    Object[] badArityArgs = (n == 2 ? null : new Object[n]);
    try { assert((boolean) eq2.invokeExact(badArityArgs) && false); }
    catch (IllegalArgumentException ex) { } // OK
  }
  // spread both arguments from a String array:
  MethodHandle eq2s = equals.asSpreader(String[].class, 2);
  assert( (boolean) eq2s.invokeExact(new String[]{ "me", "me" }));
  assert(!(boolean) eq2s.invokeExact(new String[]{ "me", "thee" }));
  // spread second arguments from a 1-array:
  MethodHandle eq1 = equals.asSpreader(Object[].class, 1);
  assert( (boolean) eq1.invokeExact("me", new Object[]{ "me" }));
  assert(!(boolean) eq1.invokeExact("me", new Object[]{ "thee" }));
  // spread no arguments from a 0-array or null:
  MethodHandle eq0 = equals.asSpreader(Object[].class, 0);
  assert( (boolean) eq0.invokeExact("me", (Object)"me", new Object[0]));
  assert(!(boolean) eq0.invokeExact("me", (Object)"thee", (Object[])null));
  // asSpreader and asCollector are approximate inverses:
  for (int n = 0; n <= 2; n++) {
      for (Class<?> a : new Class<?>[]{Object[].class, String[].class, CharSequence[].class}) {
          MethodHandle equals2 = equals.asSpreader(a, n).asCollector(a, n);
          assert( (boolean) equals2.invokeWithArguments("me", "me"));
          assert(!(boolean) equals2.invokeWithArguments("me", "thee"));
      }
  }
  MethodHandle caToString = publicLookup()
    .findStatic(Arrays.class, "toString", methodType(String.class, char[].class));
  assertEquals("[A, B, C]", (String) caToString.invokeExact("ABC".toCharArray()));
  MethodHandle caString3 = caToString.asCollector(char[].class, 3);
  assertEquals("[A, B, C]", (String) caString3.invokeExact('A', 'B', 'C'));
  MethodHandle caToString2 = caString3.asSpreader(char[].class, 2);
  assertEquals("[A, B, C]", (String) caToString2.invokeExact('A', "BC".toCharArray()));
       * }</pre></blockquote>
       * @param arrayType usually {@code Object[]}, the type of the array argument from which to extract the spread arguments
       * @param arrayLength the number of arguments to spread from an incoming array argument
       * @return a new method handle which spreads its final array argument,
       *         before calling the original method handle
       * @throws NullPointerException if {@code arrayType} is a null reference
       * @throws IllegalArgumentException if {@code arrayType} is not an array type,
       *         or if target does not have at least
       *         {@code arrayLength} parameter types,
       *         or if {@code arrayLength} is negative,
       *         or if the resulting method handle's type would have
       *         <a href="MethodHandle.html#maxarity">too many parameters</a>
       * @throws WrongMethodTypeException if the implied {@code asType} call fails
       * @see #asCollector
       */
      public MethodHandle asSpreader(Class<?> arrayType, int arrayLength) {
          MethodType postSpreadType = asSpreaderChecks(arrayType, arrayLength);
          // BEGIN Android-changed: Android specific implementation.
          /*
          int arity = type().parameterCount();
          int spreadArgPos = arity - arrayLength;
          MethodHandle afterSpread = this.asType(postSpreadType);
          BoundMethodHandle mh = afterSpread.rebind();
          LambdaForm lform = mh.editor().spreadArgumentsForm(1 + spreadArgPos, arrayType, arrayLength);
          MethodType preSpreadType = postSpreadType.replaceParameterTypes(spreadArgPos, arity, arrayType);
          return mh.copyWith(preSpreadType, lform);
          */
          final int targetParamCount = postSpreadType.parameterCount();
          MethodType dropArrayArgs = postSpreadType.dropParameterTypes(
                  (targetParamCount - arrayLength), targetParamCount);
          MethodType adapterType = dropArrayArgs.appendParameterTypes(arrayType);
  
          return new Transformers.Spreader(this, adapterType, arrayLength);
          // END Android-changed: Android specific implementation.
      }
  
      /**
       * See if {@code asSpreader} can be validly called with the given arguments.
       * Return the type of the method handle call after spreading but before conversions.
       */
      private MethodType asSpreaderChecks(Class<?> arrayType, int arrayLength) {
          spreadArrayChecks(arrayType, arrayLength);
          int nargs = type().parameterCount();
          if (nargs < arrayLength || arrayLength < 0)
              throw newIllegalArgumentException("bad spread array length");
          Class<?> arrayElement = arrayType.getComponentType();
          MethodType mtype = type();
          boolean match = true, fail = false;
          for (int i = nargs - arrayLength; i < nargs; i++) {
              Class<?> ptype = mtype.parameterType(i);
              if (ptype != arrayElement) {
                  match = false;
                  if (!MethodType.canConvert(arrayElement, ptype)) {
                      fail = true;
                      break;
                  }
              }
          }
          if (match)  return mtype;
          MethodType needType = mtype.asSpreaderType(arrayType, arrayLength);
          if (!fail)  return needType;
          // elicit an error:
          this.asType(needType);
          throw newInternalError("should not return", null);
      }
  
      private void spreadArrayChecks(Class<?> arrayType, int arrayLength) {
          Class<?> arrayElement = arrayType.getComponentType();
          if (arrayElement == null)
              throw newIllegalArgumentException("not an array type", arrayType);
          if ((arrayLength & 0x7F) != arrayLength) {
              if ((arrayLength & 0xFF) != arrayLength)
                  throw newIllegalArgumentException("array length is not legal", arrayLength);
              assert(arrayLength >= 128);
              if (arrayElement == long.class ||
                  arrayElement == double.class)
                  throw newIllegalArgumentException("array length is not legal for long[] or double[]", arrayLength);
          }
      }
  
      /**
       * Makes an <em>array-collecting</em> method handle, which accepts a given number of trailing
       * positional arguments and collects them into an array argument.
       * The new method handle adapts, as its <i>target</i>,
       * the current method handle.  The type of the adapter will be
       * the same as the type of the target, except that a single trailing
       * parameter (usually of type {@code arrayType}) is replaced by
       * {@code arrayLength} parameters whose type is element type of {@code arrayType}.
       * <p>
       * If the array type differs from the final argument type on the original target,
       * the original target is adapted to take the array type directly,
       * as if by a call to {@link #asType asType}.
       * <p>
       * When called, the adapter replaces its trailing {@code arrayLength}
       * arguments by a single new array of type {@code arrayType}, whose elements
       * comprise (in order) the replaced arguments.
       * Finally the target is called.
       * What the target eventually returns is returned unchanged by the adapter.
       * <p>
       * (The array may also be a shared constant when {@code arrayLength} is zero.)
       * <p>
       * (<em>Note:</em> The {@code arrayType} is often identical to the last
       * parameter type of the original target.
       * It is an explicit argument for symmetry with {@code asSpreader}, and also
       * to allow the target to use a simple {@code Object} as its last parameter type.)
       * <p>
       * In order to create a collecting adapter which is not restricted to a particular
       * number of collected arguments, use {@link #asVarargsCollector asVarargsCollector} instead.
       * <p>
       * Here are some examples of array-collecting method handles:
       * <blockquote><pre>{@code
  MethodHandle deepToString = publicLookup()
    .findStatic(Arrays.class, "deepToString", methodType(String.class, Object[].class));
  assertEquals("[won]",   (String) deepToString.invokeExact(new Object[]{"won"}));
  MethodHandle ts1 = deepToString.asCollector(Object[].class, 1);
  assertEquals(methodType(String.class, Object.class), ts1.type());
  //assertEquals("[won]", (String) ts1.invokeExact(         new Object[]{"won"})); //FAIL
  assertEquals("[[won]]", (String) ts1.invokeExact((Object) new Object[]{"won"}));
  // arrayType can be a subtype of Object[]
  MethodHandle ts2 = deepToString.asCollector(String[].class, 2);
  assertEquals(methodType(String.class, String.class, String.class), ts2.type());
  assertEquals("[two, too]", (String) ts2.invokeExact("two", "too"));
  MethodHandle ts0 = deepToString.asCollector(Object[].class, 0);
  assertEquals("[]", (String) ts0.invokeExact());
  // collectors can be nested, Lisp-style
  MethodHandle ts22 = deepToString.asCollector(Object[].class, 3).asCollector(String[].class, 2);
  assertEquals("[A, B, [C, D]]", ((String) ts22.invokeExact((Object)'A', (Object)"B", "C", "D")));
  // arrayType can be any primitive array type
  MethodHandle bytesToString = publicLookup()
    .findStatic(Arrays.class, "toString", methodType(String.class, byte[].class))
    .asCollector(byte[].class, 3);
  assertEquals("[1, 2, 3]", (String) bytesToString.invokeExact((byte)1, (byte)2, (byte)3));
  MethodHandle longsToString = publicLookup()
    .findStatic(Arrays.class, "toString", methodType(String.class, long[].class))
    .asCollector(long[].class, 1);
  assertEquals("[123]", (String) longsToString.invokeExact((long)123));
       * }</pre></blockquote>
       * @param arrayType often {@code Object[]}, the type of the array argument which will collect the arguments
       * @param arrayLength the number of arguments to collect into a new array argument
       * @return a new method handle which collects some trailing argument
       *         into an array, before calling the original method handle
       * @throws NullPointerException if {@code arrayType} is a null reference
       * @throws IllegalArgumentException if {@code arrayType} is not an array type
       *         or {@code arrayType} is not assignable to this method handle's trailing parameter type,
       *         or {@code arrayLength} is not a legal array size,
       *         or the resulting method handle's type would have
       *         <a href="MethodHandle.html#maxarity">too many parameters</a>
       * @throws WrongMethodTypeException if the implied {@code asType} call fails
       * @see #asSpreader
       * @see #asVarargsCollector
       */
      public MethodHandle asCollector(Class<?> arrayType, int arrayLength) {
          asCollectorChecks(arrayType, arrayLength);
          // BEGIN Android-changed: Android specific implementation.
          /*
          int collectArgPos = type().parameterCount() - 1;
          BoundMethodHandle mh = rebind();
          MethodType resultType = type().asCollectorType(arrayType, arrayLength);
          MethodHandle newArray = MethodHandleImpl.varargsArray(arrayType, arrayLength);
          LambdaForm lform = mh.editor().collectArgumentArrayForm(1 + collectArgPos, newArray);
          if (lform != null) {
              return mh.copyWith(resultType, lform);
          }
          lform = mh.editor().collectArgumentsForm(1 + collectArgPos, newArray.type().basicType());
          return mh.copyWithExtendL(resultType, lform, newArray);
          */
          return new Transformers.Collector(this, arrayType, arrayLength);
          // END Android-changed: Android specific implementation.
      }
  
      /**
       * See if {@code asCollector} can be validly called with the given arguments.
       * Return false if the last parameter is not an exact match to arrayType.
       */
      /*non-public*/ boolean asCollectorChecks(Class<?> arrayType, int arrayLength) {
          spreadArrayChecks(arrayType, arrayLength);
          int nargs = type().parameterCount();
          if (nargs != 0) {
              Class<?> lastParam = type().parameterType(nargs-1);
              if (lastParam == arrayType)  return true;
              if (lastParam.isAssignableFrom(arrayType))  return false;
          }
          throw newIllegalArgumentException("array type not assignable to trailing argument", this, arrayType);
      }
  
      /**
       * Makes a <em>variable arity</em> adapter which is able to accept
       * any number of trailing positional arguments and collect them
       * into an array argument.
       * <p>
       * The type and behavior of the adapter will be the same as
       * the type and behavior of the target, except that certain
       * {@code invoke} and {@code asType} requests can lead to
       * trailing positional arguments being collected into target's
       * trailing parameter.
       * Also, the last parameter type of the adapter will be
       * {@code arrayType}, even if the target has a different
       * last parameter type.
       * <p>
       * This transformation may return {@code this} if the method handle is
       * already of variable arity and its trailing parameter type
       * is identical to {@code arrayType}.
       * <p>
       * When called with {@link #invokeExact invokeExact}, the adapter invokes
       * the target with no argument changes.
       * (<em>Note:</em> This behavior is different from a
       * {@linkplain #asCollector fixed arity collector},
       * since it accepts a whole array of indeterminate length,
       * rather than a fixed number of arguments.)
       * <p>
       * When called with plain, inexact {@link #invoke invoke}, if the caller
       * type is the same as the adapter, the adapter invokes the target as with
       * {@code invokeExact}.
       * (This is the normal behavior for {@code invoke} when types match.)
       * <p>
       * Otherwise, if the caller and adapter arity are the same, and the
       * trailing parameter type of the caller is a reference type identical to
       * or assignable to the trailing parameter type of the adapter,
       * the arguments and return values are converted pairwise,
       * as if by {@link #asType asType} on a fixed arity
       * method handle.
       * <p>
       * Otherwise, the arities differ, or the adapter's trailing parameter
       * type is not assignable from the corresponding caller type.
       * In this case, the adapter replaces all trailing arguments from
       * the original trailing argument position onward, by
       * a new array of type {@code arrayType}, whose elements
       * comprise (in order) the replaced arguments.
       * <p>
       * The caller type must provides as least enough arguments,
       * and of the correct type, to satisfy the target's requirement for
       * positional arguments before the trailing array argument.
       * Thus, the caller must supply, at a minimum, {@code N-1} arguments,
       * where {@code N} is the arity of the target.
       * Also, there must exist conversions from the incoming arguments
       * to the target's arguments.
       * As with other uses of plain {@code invoke}, if these basic
       * requirements are not fulfilled, a {@code WrongMethodTypeException}
       * may be thrown.
       * <p>
       * In all cases, what the target eventually returns is returned unchanged by the adapter.
       * <p>
       * In the final case, it is exactly as if the target method handle were
       * temporarily adapted with a {@linkplain #asCollector fixed arity collector}
       * to the arity required by the caller type.
       * (As with {@code asCollector}, if the array length is zero,
       * a shared constant may be used instead of a new array.
       * If the implied call to {@code asCollector} would throw
       * an {@code IllegalArgumentException} or {@code WrongMethodTypeException},
       * the call to the variable arity adapter must throw
       * {@code WrongMethodTypeException}.)
       * <p>
       * The behavior of {@link #asType asType} is also specialized for
       * variable arity adapters, to maintain the invariant that
       * plain, inexact {@code invoke} is always equivalent to an {@code asType}
       * call to adjust the target type, followed by {@code invokeExact}.
       * Therefore, a variable arity adapter responds
       * to an {@code asType} request by building a fixed arity collector,
       * if and only if the adapter and requested type differ either
       * in arity or trailing argument type.
       * The resulting fixed arity collector has its type further adjusted
       * (if necessary) to the requested type by pairwise conversion,
       * as if by another application of {@code asType}.
       * <p>
       * When a method handle is obtained by executing an {@code ldc} instruction
       * of a {@code CONSTANT_MethodHandle} constant, and the target method is marked
       * as a variable arity method (with the modifier bit {@code 0x0080}),
       * the method handle will accept multiple arities, as if the method handle
       * constant were created by means of a call to {@code asVarargsCollector}.
       * <p>
       * In order to create a collecting adapter which collects a predetermined
       * number of arguments, and whose type reflects this predetermined number,
       * use {@link #asCollector asCollector} instead.
       * <p>
       * No method handle transformations produce new method handles with
       * variable arity, unless they are documented as doing so.
       * Therefore, besides {@code asVarargsCollector},
       * all methods in {@code MethodHandle} and {@code MethodHandles}
       * will return a method handle with fixed arity,
       * except in the cases where they are specified to return their original
       * operand (e.g., {@code asType} of the method handle's own type).
       * <p>
       * Calling {@code asVarargsCollector} on a method handle which is already
       * of variable arity will produce a method handle with the same type and behavior.
       * It may (or may not) return the original variable arity method handle.
       * <p>
       * Here is an example, of a list-making variable arity method handle:
       * <blockquote><pre>{@code
  MethodHandle deepToString = publicLookup()
    .findStatic(Arrays.class, "deepToString", methodType(String.class, Object[].class));
  MethodHandle ts1 = deepToString.asVarargsCollector(Object[].class);
  assertEquals("[won]",   (String) ts1.invokeExact(    new Object[]{"won"}));
  assertEquals("[won]",   (String) ts1.invoke(         new Object[]{"won"}));
  assertEquals("[won]",   (String) ts1.invoke(                      "won" ));
  assertEquals("[[won]]", (String) ts1.invoke((Object) new Object[]{"won"}));
  // findStatic of Arrays.asList(...) produces a variable arity method handle:
  MethodHandle asList = publicLookup()
    .findStatic(Arrays.class, "asList", methodType(List.class, Object[].class));
  assertEquals(methodType(List.class, Object[].class), asList.type());
  assert(asList.isVarargsCollector());
  assertEquals("[]", asList.invoke().toString());
  assertEquals("[1]", asList.invoke(1).toString());
  assertEquals("[two, too]", asList.invoke("two", "too").toString());
  String[] argv = { "three", "thee", "tee" };
  assertEquals("[three, thee, tee]", asList.invoke(argv).toString());
  assertEquals("[three, thee, tee]", asList.invoke((Object[])argv).toString());
  List ls = (List) asList.invoke((Object)argv);
  assertEquals(1, ls.size());
  assertEquals("[three, thee, tee]", Arrays.toString((Object[])ls.get(0)));
       * }</pre></blockquote>
       * <p style="font-size:smaller;">
       * <em>Discussion:</em>
       * These rules are designed as a dynamically-typed variation
       * of the Java rules for variable arity methods.
       * In both cases, callers to a variable arity method or method handle
       * can either pass zero or more positional arguments, or else pass
       * pre-collected arrays of any length.  Users should be aware of the
       * special role of the final argument, and of the effect of a
       * type match on that final argument, which determines whether
       * or not a single trailing argument is interpreted as a whole
       * array or a single element of an array to be collected.
       * Note that the dynamic type of the trailing argument has no
       * effect on this decision, only a comparison between the symbolic
       * type descriptor of the call site and the type descriptor of the method handle.)
       *
       * @param arrayType often {@code Object[]}, the type of the array argument which will collect the arguments
       * @return a new method handle which can collect any number of trailing arguments
       *         into an array, before calling the original method handle
       * @throws NullPointerException if {@code arrayType} is a null reference
       * @throws IllegalArgumentException if {@code arrayType} is not an array type
       *         or {@code arrayType} is not assignable to this method handle's trailing parameter type
       * @see #asCollector
       * @see #isVarargsCollector
       * @see #asFixedArity
       */
      public MethodHandle asVarargsCollector(Class<?> arrayType) {
          arrayType.getClass(); // explicit NPE
          boolean lastMatch = asCollectorChecks(arrayType, 0);
          if (isVarargsCollector() && lastMatch)
              return this;
          // Android-changed: Android specific implementation.
          // return MethodHandleImpl.makeVarargsCollector(this, arrayType);
          return new Transformers.VarargsCollector(this);
      }
  
      /**
       * Determines if this method handle
       * supports {@linkplain #asVarargsCollector variable arity} calls.
       * Such method handles arise from the following sources:
       * <ul>
       * <li>a call to {@linkplain #asVarargsCollector asVarargsCollector}
       * <li>a call to a {@linkplain MethodHandles.Lookup lookup method}
       *     which resolves to a variable arity Java method or constructor
       * <li>an {@code ldc} instruction of a {@code CONSTANT_MethodHandle}
       *     which resolves to a variable arity Java method or constructor
       * </ul>
       * @return true if this method handle accepts more than one arity of plain, inexact {@code invoke} calls
       * @see #asVarargsCollector
       * @see #asFixedArity
       */
      public boolean isVarargsCollector() {
          return false;
      }
  
      /**
       * Makes a <em>fixed arity</em> method handle which is otherwise
       * equivalent to the current method handle.
       * <p>
       * If the current method handle is not of
       * {@linkplain #asVarargsCollector variable arity},
       * the current method handle is returned.
       * This is true even if the current method handle
       * could not be a valid input to {@code asVarargsCollector}.
       * <p>
       * Otherwise, the resulting fixed-arity method handle has the same
       * type and behavior of the current method handle,
       * except that {@link #isVarargsCollector isVarargsCollector}
       * will be false.
       * The fixed-arity method handle may (or may not) be the
       * a previous argument to {@code asVarargsCollector}.
       * <p>
       * Here is an example, of a list-making variable arity method handle:
       * <blockquote><pre>{@code
  MethodHandle asListVar = publicLookup()
    .findStatic(Arrays.class, "asList", methodType(List.class, Object[].class))
    .asVarargsCollector(Object[].class);
  MethodHandle asListFix = asListVar.asFixedArity();
  assertEquals("[1]", asListVar.invoke(1).toString());
  Exception caught = null;
  try { asListFix.invoke((Object)1); }
  catch (Exception ex) { caught = ex; }
  assert(caught instanceof ClassCastException);
  assertEquals("[two, too]", asListVar.invoke("two", "too").toString());
  try { asListFix.invoke("two", "too"); }
  catch (Exception ex) { caught = ex; }
  assert(caught instanceof WrongMethodTypeException);
  Object[] argv = { "three", "thee", "tee" };
  assertEquals("[three, thee, tee]", asListVar.invoke(argv).toString());
  assertEquals("[three, thee, tee]", asListFix.invoke(argv).toString());
  assertEquals(1, ((List) asListVar.invoke((Object)argv)).size());
  assertEquals("[three, thee, tee]", asListFix.invoke((Object)argv).toString());
       * }</pre></blockquote>
       *
       * @return a new method handle which accepts only a fixed number of arguments
       * @see #asVarargsCollector
       * @see #isVarargsCollector
       */
      public MethodHandle asFixedArity() {
          // BEGIN Android-changed: Android specific implementation.
          // assert(!isVarargsCollector());
          // return this;
  
          MethodHandle mh = this;
          if (mh.isVarargsCollector()) {
              mh = ((Transformers.VarargsCollector) mh).asFixedArity();
          }
          assert(!mh.isVarargsCollector());
          return mh;
          // END Android-changed: Android specific implementation.
      }
  
      /**
       * Binds a value {@code x} to the first argument of a method handle, without invoking it.
       * The new method handle adapts, as its <i>target</i>,
       * the current method handle by binding it to the given argument.
       * The type of the bound handle will be
       * the same as the type of the target, except that a single leading
       * reference parameter will be omitted.
       * <p>
       * When called, the bound handle inserts the given value {@code x}
       * as a new leading argument to the target.  The other arguments are
       * also passed unchanged.
       * What the target eventually returns is returned unchanged by the bound handle.
       * <p>
       * The reference {@code x} must be convertible to the first parameter
       * type of the target.
       * <p>
       * (<em>Note:</em>  Because method handles are immutable, the target method handle
       * retains its original type and behavior.)
       * @param x  the value to bind to the first argument of the target
       * @return a new method handle which prepends the given value to the incoming
       *         argument list, before calling the original method handle
       * @throws IllegalArgumentException if the target does not have a
       *         leading parameter type that is a reference type
       * @throws ClassCastException if {@code x} cannot be converted
       *         to the leading parameter type of the target
       * @see MethodHandles#insertArguments
       */
      public MethodHandle bindTo(Object x) {
          x = type.leadingReferenceParameter().cast(x);  // throw CCE if needed
          // Android-changed: Android specific implementation.
          // return bindArgumentL(0, x);
          return new Transformers.BindTo(this, x);
      }
  
      /**
       * Returns a string representation of the method handle,
       * starting with the string {@code "MethodHandle"} and
       * ending with the string representation of the method handle's type.
       * In other words, this method returns a string equal to the value of:
       * <blockquote><pre>{@code
       * "MethodHandle" + type().toString()
       * }</pre></blockquote>
       * <p>
       * (<em>Note:</em>  Future releases of this API may add further information
       * to the string representation.
       * Therefore, the present syntax should not be parsed by applications.)
       *
       * @return a string representation of the method handle
       */
      @Override
      public String toString() {
          // Android-removed: Debugging support unused on Android.
          // if (DEBUG_METHOD_HANDLE_NAMES)  return "MethodHandle"+debugString();
          return standardString();
      }
      String standardString() {
          return "MethodHandle"+type;
      }
  
      // BEGIN Android-removed: Debugging support unused on Android.
      /*
      /** Return a string with a several lines describing the method handle structure.
       *  This string would be suitable for display in an IDE debugger.
       *
      String debugString() {
          return type+" : "+internalForm()+internalProperties();
      }
      */
      // END Android-removed: Debugging support unused on Android.
  
      // BEGIN Android-added: Android specific implementation.
      /** @hide */
      public int getHandleKind() {
          return handleKind;
      }
  
      /** @hide */
      protected void transform(EmulatedStackFrame arguments) throws Throwable {
          throw new AssertionError("MethodHandle.transform should never be called.");
      }
  
      /**
       * Creates a copy of this method handle, copying all relevant data.
       *
       * @hide
       */
      protected MethodHandle duplicate() {
          try {
              return (MethodHandle) this.clone();
          } catch (CloneNotSupportedException cnse) {
              throw new AssertionError("Subclass of Transformer is not cloneable");
          }
      }
  
      /**
       * This is the entry point for all transform calls, and dispatches to the protected
       * transform method. This layer of indirection exists purely for convenience, because
       * we can invoke-direct on a fixed ArtMethod for all transform variants.
       *
       * NOTE: If this extra layer of indirection proves to be a problem, we can get rid
       * of this layer of indirection at the cost of some additional ugliness.
       */
      private void transformInternal(EmulatedStackFrame arguments) throws Throwable {
          transform(arguments);
      }
      // END Android-added: Android specific implementation.
  
      // BEGIN Android-removed: RI implementation unused on Android.
      /*
      //// Implementation methods.
      //// Sub-classes can override these default implementations.
      //// All these methods assume arguments are already validated.
  
      // Other transforms to do:  convert, explicitCast, permute, drop, filter, fold, GWT, catch
  
      BoundMethodHandle bindArgumentL(int pos, Object value) {
          return rebind().bindArgumentL(pos, value);
      }
  
      /*non-public*
      MethodHandle setVarargs(MemberName member) throws IllegalAccessException {
          if (!member.isVarargs())  return this;
          Class<?> arrayType = type().lastParameterType();
          if (arrayType.isArray()) {
              return MethodHandleImpl.makeVarargsCollector(this, arrayType);
          }
          throw member.makeAccessException("cannot make variable arity", null);
      }
  
      /*non-public*
      MethodHandle viewAsType(MethodType newType, boolean strict) {
          // No actual conversions, just a new view of the same method.
          // Note that this operation must not produce a DirectMethodHandle,
          // because retyped DMHs, like any transformed MHs,
          // cannot be cracked into MethodHandleInfo.
          assert viewAsTypeChecks(newType, strict);
          BoundMethodHandle mh = rebind();
          assert(!((MethodHandle)mh instanceof DirectMethodHandle));
          return mh.copyWith(newType, mh.form);
      }
  
      /*non-public*
      boolean viewAsTypeChecks(MethodType newType, boolean strict) {
          if (strict) {
              assert(type().isViewableAs(newType, true))
                  : Arrays.asList(this, newType);
          } else {
              assert(type().basicType().isViewableAs(newType.basicType(), true))
                  : Arrays.asList(this, newType);
          }
          return true;
      }
  
      // Decoding
  
      /*non-public*
      LambdaForm internalForm() {
          return form;
      }
  
      /*non-public*
      MemberName internalMemberName() {
          return null;  // DMH returns DMH.member
      }
  
      /*non-public*
      Class<?> internalCallerClass() {
          return null;  // caller-bound MH for @CallerSensitive method returns caller
      }
  
      /*non-public*
      MethodHandleImpl.Intrinsic intrinsicName() {
          // no special intrinsic meaning to most MHs
          return MethodHandleImpl.Intrinsic.NONE;
      }
  
      /*non-public*
      MethodHandle withInternalMemberName(MemberName member, boolean isInvokeSpecial) {
          if (member != null) {
              return MethodHandleImpl.makeWrappedMember(this, member, isInvokeSpecial);
          } else if (internalMemberName() == null) {
              // The required internaMemberName is null, and this MH (like most) doesn't have one.
              return this;
          } else {
              // The following case is rare. Mask the internalMemberName by wrapping the MH in a BMH.
              MethodHandle result = rebind();
              assert (result.internalMemberName() == null);
              return result;
          }
      }
  
      /*non-public*
      boolean isInvokeSpecial() {
          return false;  // DMH.Special returns true
      }
  
      /*non-public*
      Object internalValues() {
          return null;
      }
  
      /*non-public*
      Object internalProperties() {
          // Override to something to follow this.form, like "\n& FOO=bar"
          return "";
      }
  
      //// Method handle implementation methods.
      //// Sub-classes can override these default implementations.
      //// All these methods assume arguments are already validated.
  
      /*non-public*
      abstract MethodHandle copyWith(MethodType mt, LambdaForm lf);
  
      /** Require this method handle to be a BMH, or else replace it with a "wrapper" BMH.
       *  Many transforms are implemented only for BMHs.
       *  @return a behaviorally equivalent BMH
       *
      abstract BoundMethodHandle rebind();
  
      /**
       * Replace the old lambda form of this method handle with a new one.
       * The new one must be functionally equivalent to the old one.
       * Threads may continue running the old form indefinitely,
       * but it is likely that the new one will be preferred for new executions.
       * Use with discretion.
       *
      /*non-public*
      void updateForm(LambdaForm newForm) {
          assert(newForm.customized == null || newForm.customized == this);
          if (form == newForm)  return;
          newForm.prepare();  // as in MethodHandle.<init>
          UNSAFE.putObject(this, FORM_OFFSET, newForm);
          UNSAFE.fullFence();
      }
  
      /** Craft a LambdaForm customized for this particular MethodHandle *
      /*non-public*
      void customize() {
          if (form.customized == null) {
              LambdaForm newForm = form.customize(this);
              updateForm(newForm);
          } else {
              assert(form.customized == this);
          }
      }
  
      private static final long FORM_OFFSET;
      static {
          try {
              FORM_OFFSET = UNSAFE.objectFieldOffset(MethodHandle.class.getDeclaredField("form"));
          } catch (ReflectiveOperationException ex) {
              throw newInternalError(ex);
          }
      }
      */
      // END Android-removed: RI implementation unused on Android.
  }
  