content: /*
   * Copyright (C) 2014 The Android Open Source Project
   * Copyright (c) 1994, 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;
  import dalvik.annotation.optimization.FastNative;
  import  java.io.*;
  import  java.util.*;
  
  /**
   * The {@code Throwable} class is the superclass of all errors and
   * exceptions in the Java language. Only objects that are instances of this
   * class (or one of its subclasses) are thrown by the Java Virtual Machine or
   * can be thrown by the Java {@code throw} statement. Similarly, only
   * this class or one of its subclasses can be the argument type in a
   * {@code catch} clause.
   *
   * For the purposes of compile-time checking of exceptions, {@code
   * Throwable} and any subclass of {@code Throwable} that is not also a
   * subclass of either {@link RuntimeException} or {@link Error} are
   * regarded as checked exceptions.
   *
   * <p>Instances of two subclasses, {@link Error} and
   * {@link Exception}, are conventionally used to indicate
   * that exceptional situations have occurred. Typically, these instances
   * are freshly created in the context of the exceptional situation so
   * as to include relevant information (such as stack trace data).
   *
   * <p>A throwable contains a snapshot of the execution stack of its
   * thread at the time it was created. It can also contain a message
   * string that gives more information about the error. Over time, a
   * throwable can {@linkplain Throwable#addSuppressed suppress} other
   * throwables from being propagated.  Finally, the throwable can also
   * contain a <i>cause</i>: another throwable that caused this
   * throwable to be constructed.  The recording of this causal information
   * is referred to as the <i>chained exception</i> facility, as the
   * cause can, itself, have a cause, and so on, leading to a "chain" of
   * exceptions, each caused by another.
   *
   * <p>One reason that a throwable may have a cause is that the class that
   * throws it is built atop a lower layered abstraction, and an operation on
   * the upper layer fails due to a failure in the lower layer.  It would be bad
   * design to let the throwable thrown by the lower layer propagate outward, as
   * it is generally unrelated to the abstraction provided by the upper layer.
   * Further, doing so would tie the API of the upper layer to the details of
   * its implementation, assuming the lower layer's exception was a checked
   * exception.  Throwing a "wrapped exception" (i.e., an exception containing a
   * cause) allows the upper layer to communicate the details of the failure to
   * its caller without incurring either of these shortcomings.  It preserves
   * the flexibility to change the implementation of the upper layer without
   * changing its API (in particular, the set of exceptions thrown by its
   * methods).
   *
   * <p>A second reason that a throwable may have a cause is that the method
   * that throws it must conform to a general-purpose interface that does not
   * permit the method to throw the cause directly.  For example, suppose
   * a persistent collection conforms to the {@link Collection
   * Collection} interface, and that its persistence is implemented atop
   * {@code java.io}.  Suppose the internals of the {@code add} method
   * can throw an {@link IOException IOException}.  The implementation
   * can communicate the details of the {@code IOException} to its caller
   * while conforming to the {@code Collection} interface by wrapping the
   * {@code IOException} in an appropriate unchecked exception.  (The
   * specification for the persistent collection should indicate that it is
   * capable of throwing such exceptions.)
   *
   * <p>A cause can be associated with a throwable in two ways: via a
   * constructor that takes the cause as an argument, or via the
   * {@link #initCause(Throwable)} method.  New throwable classes that
   * wish to allow causes to be associated with them should provide constructors
   * that take a cause and delegate (perhaps indirectly) to one of the
   * {@code Throwable} constructors that takes a cause.
   *
   * Because the {@code initCause} method is public, it allows a cause to be
   * associated with any throwable, even a "legacy throwable" whose
   * implementation predates the addition of the exception chaining mechanism to
   * {@code Throwable}.
   *
   * <p>By convention, class {@code Throwable} and its subclasses have two
   * constructors, one that takes no arguments and one that takes a
   * {@code String} argument that can be used to produce a detail message.
   * Further, those subclasses that might likely have a cause associated with
   * them should have two more constructors, one that takes a
   * {@code Throwable} (the cause), and one that takes a
   * {@code String} (the detail message) and a {@code Throwable} (the
   * cause).
   *
   * @author  unascribed
   * @author  Josh Bloch (Added exception chaining and programmatic access to
   *          stack trace in 1.4.)
   * @jls 11.2 Compile-Time Checking of Exceptions
   * @since JDK1.0
   */
  public class Throwable implements Serializable {
      /** use serialVersionUID from JDK 1.0.2 for interoperability */
      private static final long serialVersionUID = -3042686055658047285L;
  
      /**
       * Native code saves some indication of the stack backtrace in this slot.
       */
      private transient Object backtrace;
  
      /**
       * Specific details about the Throwable.  For example, for
       * {@code FileNotFoundException}, this contains the name of
       * the file that could not be found.
       *
       * @serial
       */
      private String detailMessage;
  
  
      /**
       * Holder class to defer initializing sentinel objects only used
       * for serialization.
       */
      private static class SentinelHolder {
          /**
           * {@linkplain #setStackTrace(StackTraceElement[]) Setting the
           * stack trace} to a one-element array containing this sentinel
           * value indicates future attempts to set the stack trace will be
           * ignored.  The sentinal is equal to the result of calling:<br>
           * {@code new StackTraceElement("", "", null, Integer.MIN_VALUE)}
           */
          public static final StackTraceElement STACK_TRACE_ELEMENT_SENTINEL =
              new StackTraceElement("", "", null, Integer.MIN_VALUE);
  
          /**
           * Sentinel value used in the serial form to indicate an immutable
           * stack trace.
           */
          public static final StackTraceElement[] STACK_TRACE_SENTINEL =
              new StackTraceElement[] {STACK_TRACE_ELEMENT_SENTINEL};
      }
  
      // Android-removed: Use libcore.util.EmptyArray for the empty stack trace
      // Adding the constant UNASSIGNED_STACK breaks serialization of some subclasses
      // /**
      //  * A shared value for an empty stack.
      //  */
      // private static final StackTraceElement[] UNASSIGNED_STACK = new StackTraceElement[0];
  
      /*
       * To allow Throwable objects to be made immutable and safely
       * reused by the JVM, such as OutOfMemoryErrors, fields of
       * Throwable that are writable in response to user actions, cause,
       * stackTrace, and suppressedExceptions obey the following
       * protocol:
       *
       * 1) The fields are initialized to a non-null sentinel value
       * which indicates the value has logically not been set.
       *
       * 2) Writing a null to the field indicates further writes
       * are forbidden
       *
       * 3) The sentinel value may be replaced with another non-null
       * value.
       *
       * For example, implementations of the HotSpot JVM have
       * preallocated OutOfMemoryError objects to provide for better
       * diagnosability of that situation.  These objects are created
       * without calling the constructor for that class and the fields
       * in question are initialized to null.  To support this
       * capability, any new fields added to Throwable that require
       * being initialized to a non-null value require a coordinated JVM
       * change.
       */
  
      /**
       * The throwable that caused this throwable to get thrown, or null if this
       * throwable was not caused by another throwable, or if the causative
       * throwable is unknown.  If this field is equal to this throwable itself,
       * it indicates that the cause of this throwable has not yet been
       * initialized.
       *
       * @serial
       * @since 1.4
       */
      private Throwable cause = this;
  
      /**
       * The stack trace, as returned by {@link #getStackTrace()}.
       *
       * The field is initialized to a zero-length array.  A {@code
       * null} value of this field indicates subsequent calls to {@link
       * #setStackTrace(StackTraceElement[])} and {@link
       * #fillInStackTrace()} will be be no-ops.
       *
       * @serial
       * @since 1.4
       */
      // Android-changed: Use libcore.util.EmptyArray for the empty stack trace
      // private StackTraceElement[] stackTrace = UNASSIGNED_STACK;
      private StackTraceElement[] stackTrace = libcore.util.EmptyArray.STACK_TRACE_ELEMENT;
  
      // Android-removed: Use empty collection in place of SUPPRESSED_SENTINEL
      // Adding this constant breaks serialization of some subclasses
      /*
      // Setting this static field introduces an acceptable
      // initialization dependency on a few java.util classes.
      private static final List<Throwable> SUPPRESSED_SENTINEL =
          Collections.unmodifiableList(new ArrayList<Throwable>(0));
      */
  
      /**
       * The list of suppressed exceptions, as returned by {@link
       * #getSuppressed()}.  The list is initialized to a zero-element
       * unmodifiable sentinel list.  When a serialized Throwable is
       * read in, if the {@code suppressedExceptions} field points to a
       * zero-element list, the field is reset to the sentinel value.
       *
       * @serial
       * @since 1.7
       */
      // Android-changed: Use empty collection in place of SUPPRESSED_SENTINEL
      // private List<Throwable> suppressedExceptions = SUPPRESSED_SENTINEL;
      private List<Throwable> suppressedExceptions = Collections.emptyList();
  
      /** Message for trying to suppress a null exception. */
      private static final String NULL_CAUSE_MESSAGE = "Cannot suppress a null exception.";
  
      /** Message for trying to suppress oneself. */
      private static final String SELF_SUPPRESSION_MESSAGE = "Self-suppression not permitted";
  
      /** Caption  for labeling causative exception stack traces */
      private static final String CAUSE_CAPTION = "Caused by: ";
  
      /** Caption for labeling suppressed exception stack traces */
      private static final String SUPPRESSED_CAPTION = "Suppressed: ";
  
      /**
       * Constructs a new throwable with {@code null} as its detail message.
       * The cause is not initialized, and may subsequently be initialized by a
       * call to {@link #initCause}.
       *
       * <p>The {@link #fillInStackTrace()} method is called to initialize
       * the stack trace data in the newly created throwable.
       */
      public Throwable() {
          fillInStackTrace();
      }
  
      /**
       * Constructs a new throwable with the specified detail message.  The
       * cause is not initialized, and may subsequently be initialized by
       * a call to {@link #initCause}.
       *
       * <p>The {@link #fillInStackTrace()} method is called to initialize
       * the stack trace data in the newly created throwable.
       *
       * @param   message   the detail message. The detail message is saved for
       *          later retrieval by the {@link #getMessage()} method.
       */
      public Throwable(String message) {
          fillInStackTrace();
          detailMessage = message;
      }
  
      /**
       * Constructs a new throwable with the specified detail message and
       * cause.  <p>Note that the detail message associated with
       * {@code cause} is <i>not</i> automatically incorporated in
       * this throwable's detail message.
       *
       * <p>The {@link #fillInStackTrace()} method is called to initialize
       * the stack trace data in the newly created throwable.
       *
       * @param  message the detail message (which is saved for later retrieval
       *         by the {@link #getMessage()} method).
       * @param  cause the cause (which is saved for later retrieval by the
       *         {@link #getCause()} method).  (A {@code null} value is
       *         permitted, and indicates that the cause is nonexistent or
       *         unknown.)
       * @since  1.4
       */
      public Throwable(String message, Throwable cause) {
          fillInStackTrace();
          detailMessage = message;
          this.cause = cause;
      }
  
      /**
       * Constructs a new throwable with the specified cause and a detail
       * message of {@code (cause==null ? null : cause.toString())} (which
       * typically contains the class and detail message of {@code cause}).
       * This constructor is useful for throwables that are little more than
       * wrappers for other throwables (for example, {@link
       * java.security.PrivilegedActionException}).
       *
       * <p>The {@link #fillInStackTrace()} method is called to initialize
       * the stack trace data in the newly created throwable.
       *
       * @param  cause the cause (which is saved for later retrieval by the
       *         {@link #getCause()} method).  (A {@code null} value is
       *         permitted, and indicates that the cause is nonexistent or
       *         unknown.)
       * @since  1.4
       */
      public Throwable(Throwable cause) {
          fillInStackTrace();
          detailMessage = (cause==null ? null : cause.toString());
          this.cause = cause;
      }
  
      /**
       * Constructs a new throwable with the specified detail message,
       * cause, {@linkplain #addSuppressed suppression} enabled or
       * disabled, and writable stack trace enabled or disabled.  If
       * suppression is disabled, {@link #getSuppressed} for this object
       * will return a zero-length array and calls to {@link
       * #addSuppressed} that would otherwise append an exception to the
       * suppressed list will have no effect.  If the writable stack
       * trace is false, this constructor will not call {@link
       * #fillInStackTrace()}, a {@code null} will be written to the
       * {@code stackTrace} field, and subsequent calls to {@code
       * fillInStackTrace} and {@link
       * #setStackTrace(StackTraceElement[])} will not set the stack
       * trace.  If the writable stack trace is false, {@link
       * #getStackTrace} will return a zero length array.
       *
       * <p>Note that the other constructors of {@code Throwable} treat
       * suppression as being enabled and the stack trace as being
       * writable.  Subclasses of {@code Throwable} should document any
       * conditions under which suppression is disabled and document
       * conditions under which the stack trace is not writable.
       * Disabling of suppression should only occur in exceptional
       * circumstances where special requirements exist, such as a
       * virtual machine reusing exception objects under low-memory
       * situations.  Circumstances where a given exception object is
       * repeatedly caught and rethrown, such as to implement control
       * flow between two sub-systems, is another situation where
       * immutable throwable objects would be appropriate.
       *
       * @param  message the detail message.
       * @param cause the cause.  (A {@code null} value is permitted,
       * and indicates that the cause is nonexistent or unknown.)
       * @param enableSuppression whether or not suppression is enabled or disabled
       * @param writableStackTrace whether or not the stack trace should be
       *                           writable
       *
       * @see OutOfMemoryError
       * @see NullPointerException
       * @see ArithmeticException
       * @since 1.7
       */
      protected Throwable(String message, Throwable cause,
                          boolean enableSuppression,
                          boolean writableStackTrace) {
          if (writableStackTrace) {
              fillInStackTrace();
          } else {
              stackTrace = null;
          }
          detailMessage = message;
          this.cause = cause;
          if (!enableSuppression)
              suppressedExceptions = null;
      }
  
      /**
       * Returns the detail message string of this throwable.
       *
       * @return  the detail message string of this {@code Throwable} instance
       *          (which may be {@code null}).
       */
      public String getMessage() {
          return detailMessage;
      }
  
      /**
       * Creates a localized description of this throwable.
       * Subclasses may override this method in order to produce a
       * locale-specific message.  For subclasses that do not override this
       * method, the default implementation returns the same result as
       * {@code getMessage()}.
       *
       * @return  The localized description of this throwable.
       * @since   JDK1.1
       */
      public String getLocalizedMessage() {
          return getMessage();
      }
  
      /**
       * Returns the cause of this throwable or {@code null} if the
       * cause is nonexistent or unknown.  (The cause is the throwable that
       * caused this throwable to get thrown.)
       *
       * <p>This implementation returns the cause that was supplied via one of
       * the constructors requiring a {@code Throwable}, or that was set after
       * creation with the {@link #initCause(Throwable)} method.  While it is
       * typically unnecessary to override this method, a subclass can override
       * it to return a cause set by some other means.  This is appropriate for
       * a "legacy chained throwable" that predates the addition of chained
       * exceptions to {@code Throwable}.  Note that it is <i>not</i>
       * necessary to override any of the {@code PrintStackTrace} methods,
       * all of which invoke the {@code getCause} method to determine the
       * cause of a throwable.
       *
       * @return  the cause of this throwable or {@code null} if the
       *          cause is nonexistent or unknown.
       * @since 1.4
       */
      public synchronized Throwable getCause() {
          return (cause==this ? null : cause);
      }
  
      /**
       * Initializes the <i>cause</i> of this throwable to the specified value.
       * (The cause is the throwable that caused this throwable to get thrown.)
       *
       * <p>This method can be called at most once.  It is generally called from
       * within the constructor, or immediately after creating the
       * throwable.  If this throwable was created
       * with {@link #Throwable(Throwable)} or
       * {@link #Throwable(String,Throwable)}, this method cannot be called
       * even once.
       *
       * <p>An example of using this method on a legacy throwable type
       * without other support for setting the cause is:
       *
       * <pre>
       * try {
       *     lowLevelOp();
       * } catch (LowLevelException le) {
       *     throw (HighLevelException)
       *           new HighLevelException().initCause(le); // Legacy constructor
       * }
       * </pre>
       *
       * @param  cause the cause (which is saved for later retrieval by the
       *         {@link #getCause()} method).  (A {@code null} value is
       *         permitted, and indicates that the cause is nonexistent or
       *         unknown.)
       * @return  a reference to this {@code Throwable} instance.
       * @throws IllegalArgumentException if {@code cause} is this
       *         throwable.  (A throwable cannot be its own cause.)
       * @throws IllegalStateException if this throwable was
       *         created with {@link #Throwable(Throwable)} or
       *         {@link #Throwable(String,Throwable)}, or this method has already
       *         been called on this throwable.
       * @since  1.4
       */
      public synchronized Throwable initCause(Throwable cause) {
          if (this.cause != this)
              throw new IllegalStateException("Can't overwrite cause with " +
                                              Objects.toString(cause, "a null"), this);
          if (cause == this)
              throw new IllegalArgumentException("Self-causation not permitted", this);
          this.cause = cause;
          return this;
      }
  
      /**
       * Returns a short description of this throwable.
       * The result is the concatenation of:
       * <ul>
       * <li> the {@linkplain Class#getName() name} of the class of this object
       * <li> ": " (a colon and a space)
       * <li> the result of invoking this object's {@link #getLocalizedMessage}
       *      method
       * </ul>
       * If {@code getLocalizedMessage} returns {@code null}, then just
       * the class name is returned.
       *
       * @return a string representation of this throwable.
       */
      public String toString() {
          String s = getClass().getName();
          String message = getLocalizedMessage();
          return (message != null) ? (s + ": " + message) : s;
      }
  
      /**
       * Prints this throwable and its backtrace to the
       * standard error stream. This method prints a stack trace for this
       * {@code Throwable} object on the error output stream that is
       * the value of the field {@code System.err}. The first line of
       * output contains the result of the {@link #toString()} method for
       * this object.  Remaining lines represent data previously recorded by
       * the method {@link #fillInStackTrace()}. The format of this
       * information depends on the implementation, but the following
       * example may be regarded as typical:
       * <blockquote><pre>
       * java.lang.NullPointerException
       *         at MyClass.mash(MyClass.java:9)
       *         at MyClass.crunch(MyClass.java:6)
       *         at MyClass.main(MyClass.java:3)
       * </pre></blockquote>
       * This example was produced by running the program:
       * <pre>
       * class MyClass {
       *     public static void main(String[] args) {
       *         crunch(null);
       *     }
       *     static void crunch(int[] a) {
       *         mash(a);
       *     }
       *     static void mash(int[] b) {
       *         System.out.println(b[0]);
       *     }
       * }
       * </pre>
       * The backtrace for a throwable with an initialized, non-null cause
       * should generally include the backtrace for the cause.  The format
       * of this information depends on the implementation, but the following
       * example may be regarded as typical:
       * <pre>
       * HighLevelException: MidLevelException: LowLevelException
       *         at Junk.a(Junk.java:13)
       *         at Junk.main(Junk.java:4)
       * Caused by: MidLevelException: LowLevelException
       *         at Junk.c(Junk.java:23)
       *         at Junk.b(Junk.java:17)
       *         at Junk.a(Junk.java:11)
       *         ... 1 more
       * Caused by: LowLevelException
       *         at Junk.e(Junk.java:30)
       *         at Junk.d(Junk.java:27)
       *         at Junk.c(Junk.java:21)
       *         ... 3 more
       * </pre>
       * Note the presence of lines containing the characters {@code "..."}.
       * These lines indicate that the remainder of the stack trace for this
       * exception matches the indicated number of frames from the bottom of the
       * stack trace of the exception that was caused by this exception (the
       * "enclosing" exception).  This shorthand can greatly reduce the length
       * of the output in the common case where a wrapped exception is thrown
       * from same method as the "causative exception" is caught.  The above
       * example was produced by running the program:
       * <pre>
       * public class Junk {
       *     public static void main(String args[]) {
       *         try {
       *             a();
       *         } catch(HighLevelException e) {
       *             e.printStackTrace();
       *         }
       *     }
       *     static void a() throws HighLevelException {
       *         try {
       *             b();
       *         } catch(MidLevelException e) {
       *             throw new HighLevelException(e);
       *         }
       *     }
       *     static void b() throws MidLevelException {
       *         c();
       *     }
       *     static void c() throws MidLevelException {
       *         try {
       *             d();
       *         } catch(LowLevelException e) {
       *             throw new MidLevelException(e);
       *         }
       *     }
       *     static void d() throws LowLevelException {
       *        e();
       *     }
       *     static void e() throws LowLevelException {
       *         throw new LowLevelException();
       *     }
       * }
       *
       * class HighLevelException extends Exception {
       *     HighLevelException(Throwable cause) { super(cause); }
       * }
       *
       * class MidLevelException extends Exception {
       *     MidLevelException(Throwable cause)  { super(cause); }
       * }
       *
       * class LowLevelException extends Exception {
       * }
       * </pre>
       * As of release 7, the platform supports the notion of
       * <i>suppressed exceptions</i> (in conjunction with the {@code
       * try}-with-resources statement). Any exceptions that were
       * suppressed in order to deliver an exception are printed out
       * beneath the stack trace.  The format of this information
       * depends on the implementation, but the following example may be
       * regarded as typical:
       *
       * <pre>
       * Exception in thread "main" java.lang.Exception: Something happened
       *  at Foo.bar(Foo.java:10)
       *  at Foo.main(Foo.java:5)
       *  Suppressed: Resource$CloseFailException: Resource ID = 0
       *          at Resource.close(Resource.java:26)
       *          at Foo.bar(Foo.java:9)
       *          ... 1 more
       * </pre>
       * Note that the "... n more" notation is used on suppressed exceptions
       * just at it is used on causes. Unlike causes, suppressed exceptions are
       * indented beyond their "containing exceptions."
       *
       * <p>An exception can have both a cause and one or more suppressed
       * exceptions:
       * <pre>
       * Exception in thread "main" java.lang.Exception: Main block
       *  at Foo3.main(Foo3.java:7)
       *  Suppressed: Resource$CloseFailException: Resource ID = 2
       *          at Resource.close(Resource.java:26)
       *          at Foo3.main(Foo3.java:5)
       *  Suppressed: Resource$CloseFailException: Resource ID = 1
       *          at Resource.close(Resource.java:26)
       *          at Foo3.main(Foo3.java:5)
       * Caused by: java.lang.Exception: I did it
       *  at Foo3.main(Foo3.java:8)
       * </pre>
       * Likewise, a suppressed exception can have a cause:
       * <pre>
       * Exception in thread "main" java.lang.Exception: Main block
       *  at Foo4.main(Foo4.java:6)
       *  Suppressed: Resource2$CloseFailException: Resource ID = 1
       *          at Resource2.close(Resource2.java:20)
       *          at Foo4.main(Foo4.java:5)
       *  Caused by: java.lang.Exception: Rats, you caught me
       *          at Resource2$CloseFailException.&lt;init&gt;(Resource2.java:45)
       *          ... 2 more
       * </pre>
       */
      public void printStackTrace() {
          printStackTrace(System.err);
      }
  
      /**
       * Prints this throwable and its backtrace to the specified print stream.
       *
       * @param s {@code PrintStream} to use for output
       */
      public void printStackTrace(PrintStream s) {
          printStackTrace(new WrappedPrintStream(s));
      }
  
      private void printStackTrace(PrintStreamOrWriter s) {
          // Guard against malicious overrides of Throwable.equals by
          // using a Set with identity equality semantics.
          Set<Throwable> dejaVu =
              Collections.newSetFromMap(new IdentityHashMap<Throwable, Boolean>());
          dejaVu.add(this);
  
          synchronized (s.lock()) {
              // Print our stack trace
              s.println(this);
              StackTraceElement[] trace = getOurStackTrace();
              for (StackTraceElement traceElement : trace)
                  s.println("\tat " + traceElement);
  
              // Print suppressed exceptions, if any
              for (Throwable se : getSuppressed())
                  se.printEnclosedStackTrace(s, trace, SUPPRESSED_CAPTION, "\t", dejaVu);
  
              // Print cause, if any
              Throwable ourCause = getCause();
              if (ourCause != null)
                  ourCause.printEnclosedStackTrace(s, trace, CAUSE_CAPTION, "", dejaVu);
          }
      }
  
      /**
       * Print our stack trace as an enclosed exception for the specified
       * stack trace.
       */
      private void printEnclosedStackTrace(PrintStreamOrWriter s,
                                           StackTraceElement[] enclosingTrace,
                                           String caption,
                                           String prefix,
                                           Set<Throwable> dejaVu) {
          // Android-removed: Use of assert keyword which breaks serialization of some subclasses
          // (Using assert adds a static field that determines whether assertions are enabled.)
          // assert Thread.holdsLock(s.lock());
          if (dejaVu.contains(this)) {
              s.println("\t[CIRCULAR REFERENCE:" + this + "]");
          } else {
              dejaVu.add(this);
              // Compute number of frames in common between this and enclosing trace
              StackTraceElement[] trace = getOurStackTrace();
              int m = trace.length - 1;
              int n = enclosingTrace.length - 1;
              while (m >= 0 && n >=0 && trace[m].equals(enclosingTrace[n])) {
                  m--; n--;
              }
              int framesInCommon = trace.length - 1 - m;
  
              // Print our stack trace
              s.println(prefix + caption + this);
              for (int i = 0; i <= m; i++)
                  s.println(prefix + "\tat " + trace[i]);
              if (framesInCommon != 0)
                  s.println(prefix + "\t... " + framesInCommon + " more");
  
              // Print suppressed exceptions, if any
              for (Throwable se : getSuppressed())
                  se.printEnclosedStackTrace(s, trace, SUPPRESSED_CAPTION,
                                             prefix +"\t", dejaVu);
  
              // Print cause, if any
              Throwable ourCause = getCause();
              if (ourCause != null)
                  ourCause.printEnclosedStackTrace(s, trace, CAUSE_CAPTION, prefix, dejaVu);
          }
      }
  
      /**
       * Prints this throwable and its backtrace to the specified
       * print writer.
       *
       * @param s {@code PrintWriter} to use for output
       * @since   JDK1.1
       */
      public void printStackTrace(PrintWriter s) {
          printStackTrace(new WrappedPrintWriter(s));
      }
  
      /**
       * Wrapper class for PrintStream and PrintWriter to enable a single
       * implementation of printStackTrace.
       */
      private abstract static class PrintStreamOrWriter {
          /** Returns the object to be locked when using this StreamOrWriter */
          abstract Object lock();
  
          /** Prints the specified string as a line on this StreamOrWriter */
          abstract void println(Object o);
      }
  
      private static class WrappedPrintStream extends PrintStreamOrWriter {
          private final PrintStream printStream;
  
          WrappedPrintStream(PrintStream printStream) {
              this.printStream = printStream;
          }
  
          Object lock() {
              return printStream;
          }
  
          void println(Object o) {
              printStream.println(o);
          }
      }
  
      private static class WrappedPrintWriter extends PrintStreamOrWriter {
          private final PrintWriter printWriter;
  
          WrappedPrintWriter(PrintWriter printWriter) {
              this.printWriter = printWriter;
          }
  
          Object lock() {
              return printWriter;
          }
  
          void println(Object o) {
              printWriter.println(o);
          }
      }
  
      /**
       * Fills in the execution stack trace. This method records within this
       * {@code Throwable} object information about the current state of
       * the stack frames for the current thread.
       *
       * <p>If the stack trace of this {@code Throwable} {@linkplain
       * Throwable#Throwable(String, Throwable, boolean, boolean) is not
       * writable}, calling this method has no effect.
       *
       * @return  a reference to this {@code Throwable} instance.
       * @see     Throwable#printStackTrace()
       */
      public synchronized Throwable fillInStackTrace() {
          if (stackTrace != null ||
              backtrace != null /* Out of protocol state */ ) {
              // Android-changed: Use Android-specific nativeFillInStackTrace
              // fillInStackTrace(0);
              backtrace = nativeFillInStackTrace();
              // Android-changed: Use libcore.util.EmptyArray for the empty stack trace
              // stackTrace = UNASSIGNED_STACK;
              stackTrace = libcore.util.EmptyArray.STACK_TRACE_ELEMENT;
          }
          return this;
      }
  
      // Android-changed: Use Android-specific nativeFillInStackTrace
      // private native Throwable fillInStackTrace(int dummy);
      @FastNative
      private static native Object nativeFillInStackTrace();
  
      /**
       * Provides programmatic access to the stack trace information printed by
       * {@link #printStackTrace()}.  Returns an array of stack trace elements,
       * each representing one stack frame.  The zeroth element of the array
       * (assuming the array's length is non-zero) represents the top of the
       * stack, which is the last method invocation in the sequence.  Typically,
       * this is the point at which this throwable was created and thrown.
       * The last element of the array (assuming the array's length is non-zero)
       * represents the bottom of the stack, which is the first method invocation
       * in the sequence.
       *
       * <p>Some virtual machines may, under some circumstances, omit one
       * or more stack frames from the stack trace.  In the extreme case,
       * a virtual machine that has no stack trace information concerning
       * this throwable is permitted to return a zero-length array from this
       * method.  Generally speaking, the array returned by this method will
       * contain one element for every frame that would be printed by
       * {@code printStackTrace}.  Writes to the returned array do not
       * affect future calls to this method.
       *
       * @return an array of stack trace elements representing the stack trace
       *         pertaining to this throwable.
       * @since  1.4
       */
      public StackTraceElement[] getStackTrace() {
          return getOurStackTrace().clone();
      }
  
      private synchronized StackTraceElement[] getOurStackTrace() {
          // Initialize stack trace field with information from
          // backtrace if this is the first call to this method
          // Android-changed: Use libcore.util.EmptyArray for the empty stack trace
          // if (stackTrace == UNASSIGNED_STACK ||
          if (stackTrace == libcore.util.EmptyArray.STACK_TRACE_ELEMENT ||
              (stackTrace == null && backtrace != null) /* Out of protocol state */) {
              // BEGIN Android-changed: Use Android-specific nativeGetStackTrace
              // int depth = getStackTraceDepth();
              // stackTrace = new StackTraceElement[depth];
              // for (int i=0; i < depth; i++)
              //     stackTrace[i] = getStackTraceElement(i);
              stackTrace = nativeGetStackTrace(backtrace);
              backtrace = null;
              if (stackTrace == null) {
                  return libcore.util.EmptyArray.STACK_TRACE_ELEMENT;
              }
              // END Android-changed: Use Android-specific nativeGetStackTrace
          } else if (stackTrace == null) {
              // Android-changed: Use libcore.util.EmptyArray for the empty stack trace
              // return UNASSIGNED_STACK;
              return libcore.util.EmptyArray.STACK_TRACE_ELEMENT;
          }
          return stackTrace;
      }
  
      /**
       * Sets the stack trace elements that will be returned by
       * {@link #getStackTrace()} and printed by {@link #printStackTrace()}
       * and related methods.
       *
       * This method, which is designed for use by RPC frameworks and other
       * advanced systems, allows the client to override the default
       * stack trace that is either generated by {@link #fillInStackTrace()}
       * when a throwable is constructed or deserialized when a throwable is
       * read from a serialization stream.
       *
       * <p>If the stack trace of this {@code Throwable} {@linkplain
       * Throwable#Throwable(String, Throwable, boolean, boolean) is not
       * writable}, calling this method has no effect other than
       * validating its argument.
       *
       * @param   stackTrace the stack trace elements to be associated with
       * this {@code Throwable}.  The specified array is copied by this
       * call; changes in the specified array after the method invocation
       * returns will have no affect on this {@code Throwable}'s stack
       * trace.
       *
       * @throws NullPointerException if {@code stackTrace} is
       *         {@code null} or if any of the elements of
       *         {@code stackTrace} are {@code null}
       *
       * @since  1.4
       */
      public void setStackTrace(StackTraceElement[] stackTrace) {
          // Validate argument
          StackTraceElement[] defensiveCopy = stackTrace.clone();
          for (int i = 0; i < defensiveCopy.length; i++) {
              if (defensiveCopy[i] == null)
                  throw new NullPointerException("stackTrace[" + i + "]");
          }
  
          synchronized (this) {
              if (this.stackTrace == null && // Immutable stack
                  backtrace == null) // Test for out of protocol state
                  return;
              this.stackTrace = defensiveCopy;
          }
      }
  
      // Android-removed: Unused native method getStackTraceDepth()
      // /**
      //  * Returns the number of elements in the stack trace (or 0 if the stack
      //  * trace is unavailable).
      //  *
      //  * package-protection for use by SharedSecrets.
      //  */
      // native int getStackTraceDepth();
  
      /**
       * Returns the specified element of the stack trace.
       *
       * package-protection for use by SharedSecrets.
       *
       * @param index index of the element to return.
       * @throws IndexOutOfBoundsException if {@code index < 0 ||
       *         index >= getStackTraceDepth() }
       */
      // Android-changed: Use Android-specific nativeGetStackTrace
      // native StackTraceElement getStackTraceElement(int index);
      @FastNative
      private static native StackTraceElement[] nativeGetStackTrace(Object stackState);
  
  
      /**
       * Reads a {@code Throwable} from a stream, enforcing
       * well-formedness constraints on fields.  Null entries and
       * self-pointers are not allowed in the list of {@code
       * suppressedExceptions}.  Null entries are not allowed for stack
       * trace elements.  A null stack trace in the serial form results
       * in a zero-length stack element array. A single-element stack
       * trace whose entry is equal to {@code new StackTraceElement("",
       * "", null, Integer.MIN_VALUE)} results in a {@code null} {@code
       * stackTrace} field.
       *
       * Note that there are no constraints on the value the {@code
       * cause} field can hold; both {@code null} and {@code this} are
       * valid values for the field.
       */
      private void readObject(ObjectInputStream s)
          throws IOException, ClassNotFoundException {
          s.defaultReadObject();     // read in all fields
          if (suppressedExceptions != null) {
              List<Throwable> suppressed = null;
              if (suppressedExceptions.isEmpty()) {
                  // Use the sentinel for a zero-length list
                  // Android-changed: Use empty collection in place of SUPPRESSED_SENTINEL
                  // suppressed = SUPPRESSED_SENTINEL;
                  suppressed = Collections.emptyList();
              } else { // Copy Throwables to new list
                  suppressed = new ArrayList<>(1);
                  for (Throwable t : suppressedExceptions) {
                      // Enforce constraints on suppressed exceptions in
                      // case of corrupt or malicious stream.
                      if (t == null)
                          throw new NullPointerException(NULL_CAUSE_MESSAGE);
                      if (t == this)
                          throw new IllegalArgumentException(SELF_SUPPRESSION_MESSAGE);
                      suppressed.add(t);
                  }
              }
              suppressedExceptions = suppressed;
          } // else a null suppressedExceptions field remains null
  
          /*
           * For zero-length stack traces, use a clone of
           * UNASSIGNED_STACK rather than UNASSIGNED_STACK itself to
           * allow identity comparison against UNASSIGNED_STACK in
           * getOurStackTrace.  The identity of UNASSIGNED_STACK in
           * stackTrace indicates to the getOurStackTrace method that
           * the stackTrace needs to be constructed from the information
           * in backtrace.
           */
          if (stackTrace != null) {
              if (stackTrace.length == 0) {
                  // Android-removed: clone() call not needed because of libcore.util.EmptyArray usage
                  // stackTrace = UNASSIGNED_STACK.clone();
              }  else if (stackTrace.length == 1 &&
                          // Check for the marker of an immutable stack trace
                          SentinelHolder.STACK_TRACE_ELEMENT_SENTINEL.equals(stackTrace[0])) {
                  stackTrace = null;
              } else { // Verify stack trace elements are non-null.
                  for(StackTraceElement ste : stackTrace) {
                      if (ste == null)
                          throw new NullPointerException("null StackTraceElement in serial stream. ");
                  }
              }
          } else {
              // A null stackTrace field in the serial form can result
              // from an exception serialized without that field in
              // older JDK releases; treat such exceptions as having
              // empty stack traces.
              // Android-changed: Directly create empty array instead of cloning UNASSIGNED_STACK
              // stackTrace = UNASSIGNED_STACK.clone();
              stackTrace = new StackTraceElement[0];
          }
      }
  
      /**
       * Write a {@code Throwable} object to a stream.
       *
       * A {@code null} stack trace field is represented in the serial
       * form as a one-element array whose element is equal to {@code
       * new StackTraceElement("", "", null, Integer.MIN_VALUE)}.
       */
      private synchronized void writeObject(ObjectOutputStream s)
          throws IOException {
          // Ensure that the stackTrace field is initialized to a
          // non-null value, if appropriate.  As of JDK 7, a null stack
          // trace field is a valid value indicating the stack trace
          // should not be set.
          getOurStackTrace();
  
          StackTraceElement[] oldStackTrace = stackTrace;
          try {
              if (stackTrace == null)
                  stackTrace = SentinelHolder.STACK_TRACE_SENTINEL;
              s.defaultWriteObject();
          } finally {
              stackTrace = oldStackTrace;
          }
      }
  
      /**
       * Appends the specified exception to the exceptions that were
       * suppressed in order to deliver this exception. This method is
       * thread-safe and typically called (automatically and implicitly)
       * by the {@code try}-with-resources statement.
       *
       * <p>The suppression behavior is enabled <em>unless</em> disabled
       * {@linkplain #Throwable(String, Throwable, boolean, boolean) via
       * a constructor}.  When suppression is disabled, this method does
       * nothing other than to validate its argument.
       *
       * <p>Note that when one exception {@linkplain
       * #initCause(Throwable) causes} another exception, the first
       * exception is usually caught and then the second exception is
       * thrown in response.  In other words, there is a causal
       * connection between the two exceptions.
       *
       * In contrast, there are situations where two independent
       * exceptions can be thrown in sibling code blocks, in particular
       * in the {@code try} block of a {@code try}-with-resources
       * statement and the compiler-generated {@code finally} block
       * which closes the resource.
       *
       * In these situations, only one of the thrown exceptions can be
       * propagated.  In the {@code try}-with-resources statement, when
       * there are two such exceptions, the exception originating from
       * the {@code try} block is propagated and the exception from the
       * {@code finally} block is added to the list of exceptions
       * suppressed by the exception from the {@code try} block.  As an
       * exception unwinds the stack, it can accumulate multiple
       * suppressed exceptions.
       *
       * <p>An exception may have suppressed exceptions while also being
       * caused by another exception.  Whether or not an exception has a
       * cause is semantically known at the time of its creation, unlike
       * whether or not an exception will suppress other exceptions
       * which is typically only determined after an exception is
       * thrown.
       *
       * <p>Note that programmer written code is also able to take
       * advantage of calling this method in situations where there are
       * multiple sibling exceptions and only one can be propagated.
       *
       * @param exception the exception to be added to the list of
       *        suppressed exceptions
       * @throws IllegalArgumentException if {@code exception} is this
       *         throwable; a throwable cannot suppress itself.
       * @throws NullPointerException if {@code exception} is {@code null}
       * @since 1.7
       */
      public final synchronized void addSuppressed(Throwable exception) {
          if (exception == this)
              throw new IllegalArgumentException(SELF_SUPPRESSION_MESSAGE, exception);
  
          if (exception == null)
              throw new NullPointerException(NULL_CAUSE_MESSAGE);
  
          if (suppressedExceptions == null) // Suppressed exceptions not recorded
              return;
  
          // Android-changed: Use empty collection in place of SUPPRESSED_SENTINEL
          // if (suppressedExceptions == SUPPRESSED_SENTINEL)
          if (suppressedExceptions.isEmpty())
              suppressedExceptions = new ArrayList<>(1);
  
          suppressedExceptions.add(exception);
      }
  
      // Android-changed: Lazily initialize EMPTY_THROWABLE_ARRAY
      // private static final Throwable[] EMPTY_THROWABLE_ARRAY = new Throwable[0];
      private static Throwable[] EMPTY_THROWABLE_ARRAY;
  
      /**
       * Returns an array containing all of the exceptions that were
       * suppressed, typically by the {@code try}-with-resources
       * statement, in order to deliver this exception.
       *
       * If no exceptions were suppressed or {@linkplain
       * #Throwable(String, Throwable, boolean, boolean) suppression is
       * disabled}, an empty array is returned.  This method is
       * thread-safe.  Writes to the returned array do not affect future
       * calls to this method.
       *
       * @return an array containing all of the exceptions that were
       *         suppressed to deliver this exception.
       * @since 1.7
       */
      public final synchronized Throwable[] getSuppressed() {
          // Android-added: Lazily initialize EMPTY_THROWABLE_ARRAY
          if (EMPTY_THROWABLE_ARRAY == null) {
              EMPTY_THROWABLE_ARRAY = new Throwable[0];
          }
  
          // Android-changed: Use empty collection in place of SUPPRESSED_SENTINEL
          // if (suppressedExceptions == SUPPRESSED_SENTINEL ||
          //    suppressedExceptions == null)
          if (suppressedExceptions == null || suppressedExceptions.isEmpty())
              return EMPTY_THROWABLE_ARRAY;
          else
              return suppressedExceptions.toArray(EMPTY_THROWABLE_ARRAY);
      }
  }
  