content: /*
   * Copyright (C) 2014 The Android Open Source Project
   * Copyright (c) 1994, 2012, 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;
  
  /**
   * Class {@code Object} is the root of the class hierarchy.
   * Every class has {@code Object} as a superclass. All objects,
   * including arrays, implement the methods of this class.
   *
   * @author  unascribed
   * @see     Class
   * @since   JDK1.0
   */
  public class Object {
  
      // Android-removed: registerNatives() not used on Android
      // private static native void registerNatives();
      // static {
      //     registerNatives();
      // }
  
      // Android-added: Use Android specific fields for Class and monitor.
      private transient Class<?> shadow$_klass_;
      private transient int shadow$_monitor_;
  
      /**
       * Returns the runtime class of this {@code Object}. The returned
       * {@code Class} object is the object that is locked by {@code
       * static synchronized} methods of the represented class.
       *
       * <p><b>The actual result type is {@code Class<? extends |X|>}
       * where {@code |X|} is the erasure of the static type of the
       * expression on which {@code getClass} is called.</b> For
       * example, no cast is required in this code fragment:</p>
       *
       * <p>
       * {@code Number n = 0;                             }<br>
       * {@code Class<? extends Number> c = n.getClass(); }
       * </p>
       *
       * @return The {@code Class} object that represents the runtime
       *         class of this object.
       * @jls 15.8.2 Class Literals
       */
      // Android-changed: Use Android specific fields for Class and monitor.
      // public final native Class<?> getClass();
      public final Class<?> getClass() {
        return shadow$_klass_;
      }
  
      /**
       * Returns a hash code value for the object. This method is
       * supported for the benefit of hash tables such as those provided by
       * {@link java.util.HashMap}.
       * <p>
       * The general contract of {@code hashCode} is:
       * <ul>
       * <li>Whenever it is invoked on the same object more than once during
       *     an execution of a Java application, the {@code hashCode} method
       *     must consistently return the same integer, provided no information
       *     used in {@code equals} comparisons on the object is modified.
       *     This integer need not remain consistent from one execution of an
       *     application to another execution of the same application.
       * <li>If two objects are equal according to the {@code equals(Object)}
       *     method, then calling the {@code hashCode} method on each of
       *     the two objects must produce the same integer result.
       * <li>It is <em>not</em> required that if two objects are unequal
       *     according to the {@link Object#equals(Object)}
       *     method, then calling the {@code hashCode} method on each of the
       *     two objects must produce distinct integer results.  However, the
       *     programmer should be aware that producing distinct integer results
       *     for unequal objects may improve the performance of hash tables.
       * </ul>
       * <p>
       * As much as is reasonably practical, the hashCode method defined by
       * class {@code Object} does return distinct integers for distinct
       * objects. (This is typically implemented by converting the internal
       * address of the object into an integer, but this implementation
       * technique is not required by the
       * Java&trade; programming language.)
       *
       * @return  a hash code value for this object.
       * @see     Object#equals(Object)
       * @see     System#identityHashCode
       */
      // BEGIN Android-changed: Added a local helper for identityHashCode.
      // public native int hashCode();
      public int hashCode() {
          return identityHashCode(this);
      }
  
      // Package-private to be used by j.l.System. We do the implementation here
      // to avoid Object.hashCode doing a clinit check on j.l.System, and also
      // to avoid leaking shadow$_monitor_ outside of this class.
      /* package-private */ static int identityHashCode(Object obj) {
          int lockWord = obj.shadow$_monitor_;
          final int lockWordStateMask = 0xC0000000;  // Top 2 bits.
          final int lockWordStateHash = 0x80000000;  // Top 2 bits are value 2 (kStateHash).
          final int lockWordHashMask = 0x0FFFFFFF;  // Low 28 bits.
          if ((lockWord & lockWordStateMask) == lockWordStateHash) {
              return lockWord & lockWordHashMask;
          }
          return identityHashCodeNative(obj);
      }
  
      /**
       * Return the identity hash code when the information in the monitor field
       * is not sufficient.
       */
      @FastNative
      private static native int identityHashCodeNative(Object obj);
      // END Android-changed: Added a local helper for identityHashCode.
  
      /**
       * Indicates whether some other object is "equal to" this one.
       * <p>
       * The {@code equals} method implements an equivalence relation
       * on non-null object references:
       * <ul>
       * <li>It is <i>reflexive</i>: for any non-null reference value
       *     {@code x}, {@code x.equals(x)} should return
       *     {@code true}.
       * <li>It is <i>symmetric</i>: for any non-null reference values
       *     {@code x} and {@code y}, {@code x.equals(y)}
       *     should return {@code true} if and only if
       *     {@code y.equals(x)} returns {@code true}.
       * <li>It is <i>transitive</i>: for any non-null reference values
       *     {@code x}, {@code y}, and {@code z}, if
       *     {@code x.equals(y)} returns {@code true} and
       *     {@code y.equals(z)} returns {@code true}, then
       *     {@code x.equals(z)} should return {@code true}.
       * <li>It is <i>consistent</i>: for any non-null reference values
       *     {@code x} and {@code y}, multiple invocations of
       *     {@code x.equals(y)} consistently return {@code true}
       *     or consistently return {@code false}, provided no
       *     information used in {@code equals} comparisons on the
       *     objects is modified.
       * <li>For any non-null reference value {@code x},
       *     {@code x.equals(null)} should return {@code false}.
       * </ul>
       * <p>
       * The {@code equals} method for class {@code Object} implements
       * the most discriminating possible equivalence relation on objects;
       * that is, for any non-null reference values {@code x} and
       * {@code y}, this method returns {@code true} if and only
       * if {@code x} and {@code y} refer to the same object
       * ({@code x == y} has the value {@code true}).
       * <p>
       * Note that it is generally necessary to override the {@code hashCode}
       * method whenever this method is overridden, so as to maintain the
       * general contract for the {@code hashCode} method, which states
       * that equal objects must have equal hash codes.
       *
       * @param   obj   the reference object with which to compare.
       * @return  {@code true} if this object is the same as the obj
       *          argument; {@code false} otherwise.
       * @see     #hashCode()
       * @see     java.util.HashMap
       */
      public boolean equals(Object obj) {
          return (this == obj);
      }
  
      /**
       * Creates and returns a copy of this object.  The precise meaning
       * of "copy" may depend on the class of the object. The general
       * intent is that, for any object {@code x}, the expression:
       * <blockquote>
       * <pre>
       * x.clone() != x</pre></blockquote>
       * will be true, and that the expression:
       * <blockquote>
       * <pre>
       * x.clone().getClass() == x.getClass()</pre></blockquote>
       * will be {@code true}, but these are not absolute requirements.
       * While it is typically the case that:
       * <blockquote>
       * <pre>
       * x.clone().equals(x)</pre></blockquote>
       * will be {@code true}, this is not an absolute requirement.
       * <p>
       * By convention, the returned object should be obtained by calling
       * {@code super.clone}.  If a class and all of its superclasses (except
       * {@code Object}) obey this convention, it will be the case that
       * {@code x.clone().getClass() == x.getClass()}.
       * <p>
       * By convention, the object returned by this method should be independent
       * of this object (which is being cloned).  To achieve this independence,
       * it may be necessary to modify one or more fields of the object returned
       * by {@code super.clone} before returning it.  Typically, this means
       * copying any mutable objects that comprise the internal "deep structure"
       * of the object being cloned and replacing the references to these
       * objects with references to the copies.  If a class contains only
       * primitive fields or references to immutable objects, then it is usually
       * the case that no fields in the object returned by {@code super.clone}
       * need to be modified.
       * <p>
       * The method {@code clone} for class {@code Object} performs a
       * specific cloning operation. First, if the class of this object does
       * not implement the interface {@code Cloneable}, then a
       * {@code CloneNotSupportedException} is thrown. Note that all arrays
       * are considered to implement the interface {@code Cloneable} and that
       * the return type of the {@code clone} method of an array type {@code T[]}
       * is {@code T[]} where T is any reference or primitive type.
       * Otherwise, this method creates a new instance of the class of this
       * object and initializes all its fields with exactly the contents of
       * the corresponding fields of this object, as if by assignment; the
       * contents of the fields are not themselves cloned. Thus, this method
       * performs a "shallow copy" of this object, not a "deep copy" operation.
       * <p>
       * The class {@code Object} does not itself implement the interface
       * {@code Cloneable}, so calling the {@code clone} method on an object
       * whose class is {@code Object} will result in throwing an
       * exception at run time.
       *
       * @return     a clone of this instance.
       * @throws  CloneNotSupportedException  if the object's class does not
       *               support the {@code Cloneable} interface. Subclasses
       *               that override the {@code clone} method can also
       *               throw this exception to indicate that an instance cannot
       *               be cloned.
       * @see Cloneable
       */
      // BEGIN Android-changed: Use native local helper for clone()
      // Checks whether cloning is allowed before calling native local helper.
      // protected native Object clone() throws CloneNotSupportedException;
      protected Object clone() throws CloneNotSupportedException {
          if (!(this instanceof Cloneable)) {
              throw new CloneNotSupportedException("Class " + getClass().getName() +
                                                   " doesn't implement Cloneable");
          }
  
          return internalClone();
      }
  
      /*
       * Native helper method for cloning.
       */
      @FastNative
      private native Object internalClone();
      // END Android-changed: Use native local helper for clone()
  
      /**
       * Returns a string representation of the object. In general, the
       * {@code toString} method returns a string that
       * "textually represents" this object. The result should
       * be a concise but informative representation that is easy for a
       * person to read.
       * It is recommended that all subclasses override this method.
       * <p>
       * The {@code toString} method for class {@code Object}
       * returns a string consisting of the name of the class of which the
       * object is an instance, the at-sign character `{@code @}', and
       * the unsigned hexadecimal representation of the hash code of the
       * object. In other words, this method returns a string equal to the
       * value of:
       * <blockquote>
       * <pre>
       * getClass().getName() + '@' + Integer.toHexString(hashCode())
       * </pre></blockquote>
       *
       * @return  a string representation of the object.
       */
      public String toString() {
          return getClass().getName() + "@" + Integer.toHexString(hashCode());
      }
  
      /**
       * Wakes up a single thread that is waiting on this object's
       * monitor. If any threads are waiting on this object, one of them
       * is chosen to be awakened. The choice is arbitrary and occurs at
       * the discretion of the implementation. A thread waits on an object's
       * monitor by calling one of the {@code wait} methods.
       * <p>
       * The awakened thread will not be able to proceed until the current
       * thread relinquishes the lock on this object. The awakened thread will
       * compete in the usual manner with any other threads that might be
       * actively competing to synchronize on this object; for example, the
       * awakened thread enjoys no reliable privilege or disadvantage in being
       * the next thread to lock this object.
       * <p>
       * This method should only be called by a thread that is the owner
       * of this object's monitor. A thread becomes the owner of the
       * object's monitor in one of three ways:
       * <ul>
       * <li>By executing a synchronized instance method of that object.
       * <li>By executing the body of a {@code synchronized} statement
       *     that synchronizes on the object.
       * <li>For objects of type {@code Class,} by executing a
       *     synchronized static method of that class.
       * </ul>
       * <p>
       * Only one thread at a time can own an object's monitor.
       *
       * @throws  IllegalMonitorStateException  if the current thread is not
       *               the owner of this object's monitor.
       * @see        Object#notifyAll()
       * @see        Object#wait()
       */
      @FastNative
      public final native void notify();
  
      /**
       * Wakes up all threads that are waiting on this object's monitor. A
       * thread waits on an object's monitor by calling one of the
       * {@code wait} methods.
       * <p>
       * The awakened threads will not be able to proceed until the current
       * thread relinquishes the lock on this object. The awakened threads
       * will compete in the usual manner with any other threads that might
       * be actively competing to synchronize on this object; for example,
       * the awakened threads enjoy no reliable privilege or disadvantage in
       * being the next thread to lock this object.
       * <p>
       * This method should only be called by a thread that is the owner
       * of this object's monitor. See the {@code notify} method for a
       * description of the ways in which a thread can become the owner of
       * a monitor.
       *
       * @throws  IllegalMonitorStateException  if the current thread is not
       *               the owner of this object's monitor.
       * @see        Object#notify()
       * @see        Object#wait()
       */
      @FastNative
      public final native void notifyAll();
  
      /**
       * Causes the current thread to wait until either another thread invokes the
       * {@link Object#notify()} method or the
       * {@link Object#notifyAll()} method for this object, or a
       * specified amount of time has elapsed.
       * <p>
       * The current thread must own this object's monitor.
       * <p>
       * This method causes the current thread (call it <var>T</var>) to
       * place itself in the wait set for this object and then to relinquish
       * any and all synchronization claims on this object. Thread <var>T</var>
       * becomes disabled for thread scheduling purposes and lies dormant
       * until one of four things happens:
       * <ul>
       * <li>Some other thread invokes the {@code notify} method for this
       * object and thread <var>T</var> happens to be arbitrarily chosen as
       * the thread to be awakened.
       * <li>Some other thread invokes the {@code notifyAll} method for this
       * object.
       * <li>Some other thread {@linkplain Thread#interrupt() interrupts}
       * thread <var>T</var>.
       * <li>The specified amount of real time has elapsed, more or less.  If
       * {@code timeout} is zero, however, then real time is not taken into
       * consideration and the thread simply waits until notified.
       * </ul>
       * The thread <var>T</var> is then removed from the wait set for this
       * object and re-enabled for thread scheduling. It then competes in the
       * usual manner with other threads for the right to synchronize on the
       * object; once it has gained control of the object, all its
       * synchronization claims on the object are restored to the status quo
       * ante - that is, to the situation as of the time that the {@code wait}
       * method was invoked. Thread <var>T</var> then returns from the
       * invocation of the {@code wait} method. Thus, on return from the
       * {@code wait} method, the synchronization state of the object and of
       * thread {@code T} is exactly as it was when the {@code wait} method
       * was invoked.
       * <p>
       * A thread can also wake up without being notified, interrupted, or
       * timing out, a so-called <i>spurious wakeup</i>.  While this will rarely
       * occur in practice, applications must guard against it by testing for
       * the condition that should have caused the thread to be awakened, and
       * continuing to wait if the condition is not satisfied.  In other words,
       * waits should always occur in loops, like this one:
       * <pre>
       *     synchronized (obj) {
       *         while (&lt;condition does not hold&gt;)
       *             obj.wait(timeout);
       *         ... // Perform action appropriate to condition
       *     }
       * </pre>
       * (For more information on this topic, see Section 3.2.3 in Doug Lea's
       * "Concurrent Programming in Java (Second Edition)" (Addison-Wesley,
       * 2000), or Item 50 in Joshua Bloch's "Effective Java Programming
       * Language Guide" (Addison-Wesley, 2001).
       *
       * <p>If the current thread is {@linkplain Thread#interrupt()
       * interrupted} by any thread before or while it is waiting, then an
       * {@code InterruptedException} is thrown.  This exception is not
       * thrown until the lock status of this object has been restored as
       * described above.
       *
       * <p>
       * Note that the {@code wait} method, as it places the current thread
       * into the wait set for this object, unlocks only this object; any
       * other objects on which the current thread may be synchronized remain
       * locked while the thread waits.
       * <p>
       * This method should only be called by a thread that is the owner
       * of this object's monitor. See the {@code notify} method for a
       * description of the ways in which a thread can become the owner of
       * a monitor.
       *
       * @param      timeout   the maximum time to wait in milliseconds.
       * @throws  IllegalArgumentException      if the value of timeout is
       *               negative.
       * @throws  IllegalMonitorStateException  if the current thread is not
       *               the owner of the object's monitor.
       * @throws  InterruptedException if any thread interrupted the
       *             current thread before or while the current thread
       *             was waiting for a notification.  The <i>interrupted
       *             status</i> of the current thread is cleared when
       *             this exception is thrown.
       * @see        Object#notify()
       * @see        Object#notifyAll()
       */
      // Android-changed: Implement wait(long) non-natively.
      // public final native void wait(long timeout) throws InterruptedException;
      public final void wait(long timeout) throws InterruptedException {
          wait(timeout, 0);
      }
  
      /**
       * Causes the current thread to wait until another thread invokes the
       * {@link Object#notify()} method or the
       * {@link Object#notifyAll()} method for this object, or
       * some other thread interrupts the current thread, or a certain
       * amount of real time has elapsed.
       * <p>
       * This method is similar to the {@code wait} method of one
       * argument, but it allows finer control over the amount of time to
       * wait for a notification before giving up. The amount of real time,
       * measured in nanoseconds, is given by:
       * <blockquote>
       * <pre>
       * 1000000*timeout+nanos</pre></blockquote>
       * <p>
       * In all other respects, this method does the same thing as the
       * method {@link #wait(long)} of one argument. In particular,
       * {@code wait(0, 0)} means the same thing as {@code wait(0)}.
       * <p>
       * The current thread must own this object's monitor. The thread
       * releases ownership of this monitor and waits until either of the
       * following two conditions has occurred:
       * <ul>
       * <li>Another thread notifies threads waiting on this object's monitor
       *     to wake up either through a call to the {@code notify} method
       *     or the {@code notifyAll} method.
       * <li>The timeout period, specified by {@code timeout}
       *     milliseconds plus {@code nanos} nanoseconds arguments, has
       *     elapsed.
       * </ul>
       * <p>
       * The thread then waits until it can re-obtain ownership of the
       * monitor and resumes execution.
       * <p>
       * As in the one argument version, interrupts and spurious wakeups are
       * possible, and this method should always be used in a loop:
       * <pre>
       *     synchronized (obj) {
       *         while (&lt;condition does not hold&gt;)
       *             obj.wait(timeout, nanos);
       *         ... // Perform action appropriate to condition
       *     }
       * </pre>
       * This method should only be called by a thread that is the owner
       * of this object's monitor. See the {@code notify} method for a
       * description of the ways in which a thread can become the owner of
       * a monitor.
       *
       * @param      timeout   the maximum time to wait in milliseconds.
       * @param      nanos      additional time, in nanoseconds range
       *                       0-999999.
       * @throws  IllegalArgumentException      if the value of timeout is
       *                      negative or the value of nanos is
       *                      not in the range 0-999999.
       * @throws  IllegalMonitorStateException  if the current thread is not
       *               the owner of this object's monitor.
       * @throws  InterruptedException if any thread interrupted the
       *             current thread before or while the current thread
       *             was waiting for a notification.  The <i>interrupted
       *             status</i> of the current thread is cleared when
       *             this exception is thrown.
       */
      // Android-changed: Implement wait(long, int) natively.
      /*
      public final void wait(long timeout, int nanos) throws InterruptedException {
          if (timeout < 0) {
              throw new IllegalArgumentException("timeout value is negative");
          }
  
          if (nanos < 0 || nanos > 999999) {
              throw new IllegalArgumentException(
                                  "nanosecond timeout value out of range");
          }
  
          if (nanos > 0) {
              timeout++;
          }
  
          wait(timeout);
      }
      */
      @FastNative
      public final native void wait(long timeout, int nanos) throws InterruptedException;
  
      /**
       * Causes the current thread to wait until another thread invokes the
       * {@link Object#notify()} method or the
       * {@link Object#notifyAll()} method for this object.
       * In other words, this method behaves exactly as if it simply
       * performs the call {@code wait(0)}.
       * <p>
       * The current thread must own this object's monitor. The thread
       * releases ownership of this monitor and waits until another thread
       * notifies threads waiting on this object's monitor to wake up
       * either through a call to the {@code notify} method or the
       * {@code notifyAll} method. The thread then waits until it can
       * re-obtain ownership of the monitor and resumes execution.
       * <p>
       * As in the one argument version, interrupts and spurious wakeups are
       * possible, and this method should always be used in a loop:
       * <pre>
       *     synchronized (obj) {
       *         while (&lt;condition does not hold&gt;)
       *             obj.wait();
       *         ... // Perform action appropriate to condition
       *     }
       * </pre>
       * This method should only be called by a thread that is the owner
       * of this object's monitor. See the {@code notify} method for a
       * description of the ways in which a thread can become the owner of
       * a monitor.
       *
       * @throws  IllegalMonitorStateException  if the current thread is not
       *               the owner of the object's monitor.
       * @throws  InterruptedException if any thread interrupted the
       *             current thread before or while the current thread
       *             was waiting for a notification.  The <i>interrupted
       *             status</i> of the current thread is cleared when
       *             this exception is thrown.
       * @see        Object#notify()
       * @see        Object#notifyAll()
       */
      public final void wait() throws InterruptedException {
          wait(0);
      }
  
      /**
       * Called by the garbage collector on an object when garbage collection
       * determines that there are no more references to the object.
       * A subclass overrides the {@code finalize} method to dispose of
       * system resources or to perform other cleanup.
       * <p>
       * The general contract of {@code finalize} is that it is invoked
       * if and when the Java&trade; virtual
       * machine has determined that there is no longer any
       * means by which this object can be accessed by any thread that has
       * not yet died, except as a result of an action taken by the
       * finalization of some other object or class which is ready to be
       * finalized. The {@code finalize} method may take any action, including
       * making this object available again to other threads; the usual purpose
       * of {@code finalize}, however, is to perform cleanup actions before
       * the object is irrevocably discarded. For example, the finalize method
       * for an object that represents an input/output connection might perform
       * explicit I/O transactions to break the connection before the object is
       * permanently discarded.
       * <p>
       * The {@code finalize} method of class {@code Object} performs no
       * special action; it simply returns normally. Subclasses of
       * {@code Object} may override this definition.
       * <p>
       * The Java programming language does not guarantee which thread will
       * invoke the {@code finalize} method for any given object. It is
       * guaranteed, however, that the thread that invokes finalize will not
       * be holding any user-visible synchronization locks when finalize is
       * invoked. If an uncaught exception is thrown by the finalize method,
       * the exception is ignored and finalization of that object terminates.
       * <p>
       * After the {@code finalize} method has been invoked for an object, no
       * further action is taken until the Java virtual machine has again
       * determined that there is no longer any means by which this object can
       * be accessed by any thread that has not yet died, including possible
       * actions by other objects or classes which are ready to be finalized,
       * at which point the object may be discarded.
       * <p>
       * The {@code finalize} method is never invoked more than once by a Java
       * virtual machine for any given object.
       * <p>
       * Any exception thrown by the {@code finalize} method causes
       * the finalization of this object to be halted, but is otherwise
       * ignored.
       *
       * @throws Throwable the {@code Exception} raised by this method
       * @see java.lang.ref.WeakReference
       * @see java.lang.ref.PhantomReference
       * @jls 12.6 Finalization of Class Instances
       */
      protected void finalize() throws Throwable { }
  }
  