object.java

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   *  <li><code>o.equals(o)</code> is true</li>
   * </ul>
   *
   * <p>However, these are not strict requirements, and may
   * be violated if necessary.  Of the three requirements, the
   * last is the most commonly violated, particularly if the
   * subclass does not override {@link #equals(Object)}.
   *
   * <p>If the Object you call clone() on does not implement
   * {@link Cloneable} (which is a placeholder interface), then
   * a CloneNotSupportedException is thrown.  Notice that
   * Object does not implement Cloneable; this method exists
   * as a convenience for subclasses that do.
   *
   * <p>Object's implementation of clone allocates space for the
   * new Object using the correct class, without calling any
   * constructors, and then fills in all of the new field values
   * with the old field values.  Thus, it is a shallow copy.
   * However, subclasses are permitted to make a deep copy.
   *
   * <p>All array types implement Cloneable, and override
   * this method as follows (it should never fail):<br>
   * <pre>
   * public Object clone()
   * {
   *   try
   *     {
   *       super.clone();
   *     }
   *   catch (CloneNotSupportedException e)
   *     {
   *       throw new InternalError(e.getMessage());
   *     }
   * }
   * </pre>
   *
   * @return a copy of the Object
   * @throws CloneNotSupportedException If this Object does not
   *         implement Cloneable
   * @throws OutOfMemoryError Since cloning involves memory allocation,
   *         even though it may bypass constructors, you might run
   *         out of memory
   * @see Cloneable
   */
  protected Object clone() throws CloneNotSupportedException
  {
    if (this instanceof Cloneable)
      return VMObject.clone((Cloneable) this);
    throw new CloneNotSupportedException("Object not cloneable");
  }

  /**
   * Returns the runtime {@link Class} of this Object.
   *
   * <p>The class object can also be obtained without a runtime
   * instance by using the class literal, as in:
   * <code>Foo.class</code>.  Notice that the class literal
   * also works on primitive types, making it useful for
   * reflection purposes.
   *
   * @return the class of this Object
   */
  public final Class getClass()
  {
    return VMObject.getClass(this);
  }

  /**
   * Wakes up one of the {@link Thread}s that has called
   * <code>wait</code> on this Object.  Only the owner
   * of a lock on this Object may call this method.  This lock
   * is obtained by a <code>synchronized</code> method or statement.
   *
   * <p>The Thread to wake up is chosen arbitrarily.  The
   * awakened thread is not guaranteed to be the next thread
   * to actually obtain the lock on this object.
   *
   * <p>This thread still holds a lock on the object, so it is
   * typical to release the lock by exiting the synchronized
   * code, calling wait(), or calling {@link Thread#sleep(long)}, so
   * that the newly awakened thread can actually resume.  The
   * awakened thread will most likely be awakened with an
   * {@link InterruptedException}, but that is not guaranteed.
   *
   * @throws IllegalMonitorStateException if this Thread
   *         does not own the lock on the Object
   * @see #notifyAll()
   * @see #wait()
   * @see #wait(long)
   * @see #wait(long, int)
   * @see Thread
   */
  public final void notify() throws IllegalMonitorStateException
  {
    VMObject.notify(this);
  }

  /**
   * Wakes up all of the {@link Thread}s that have called
   * <code>wait</code> on this Object.  Only the owner
   * of a lock on this Object may call this method.  This lock
   * is obtained by a <code>synchronized</code> method or statement.
   *
   * <p>There are no guarantees as to which thread will next
   * obtain the lock on the object.
   *
   * <p>This thread still holds a lock on the object, so it is
   * typical to release the lock by exiting the synchronized
   * code, calling wait(), or calling {@link Thread#sleep(long)}, so
   * that one of the newly awakened threads can actually resume.
   * The resuming thread will most likely be awakened with an
   * {@link InterruptedException}, but that is not guaranteed.
   *
   * @throws IllegalMonitorStateException if this Thread
   *         does not own the lock on the Object
   * @see #notify()
   * @see #wait()
   * @see #wait(long)
   * @see #wait(long, int)
   * @see Thread
   */
  public final void notifyAll() throws IllegalMonitorStateException
  {
    VMObject.notifyAll(this);
  }

  /**
   * Waits indefinitely for notify() or notifyAll() to be
   * called on the Object in question.  Implementation is
   * identical to wait(0).
   *
   * <p>The Thread that calls wait must have a lock on this Object,
   * obtained by a <code>synchronized</code> method or statement.
   * After calling wait, the thread loses the lock on this
   * object until the method completes (abruptly or normally),
   * at which time it regains the lock.  All locks held on
   * other objects remain in force, even though the thread is
   * inactive. Therefore, caution must be used to avoid deadlock.
   *
   * <p>While it is typical that this method will complete abruptly
   * with an {@link InterruptedException}, it is not guaranteed.  So,
   * it is typical to call wait inside an infinite loop:<br>
   *
   * <pre>
   * try
   *   {
   *     while (true)
   *       lock.wait();
   *   }
   * catch (InterruptedException e)
   *   {
   *   }
   * </pre>
   *
   * @throws IllegalMonitorStateException if this Thread
   *         does not own a lock on this Object
   * @throws InterruptedException if some other Thread
   *         interrupts this Thread
   * @see #notify()
   * @see #notifyAll()
   * @see #wait(long)
   * @see #wait(long, int)
   * @see Thread
   */
  public final void wait()
    throws IllegalMonitorStateException, InterruptedException
  {
    VMObject.wait(this, 0, 0);
  }

  /**
   * Waits a specified amount of time (or indefinitely if
   * the time specified is 0) for someone to call notify()
   * or notifyAll() on this Object, waking up this Thread.
   *
   * <p>The Thread that calls wait must have a lock on this Object,
   * obtained by a <code>synchronized</code> method or statement.
   * After calling wait, the thread loses the lock on this
   * object until the method completes (abruptly or normally),
   * at which time it regains the lock.  All locks held on
   * other objects remain in force, even though the thread is
   * inactive. Therefore, caution must be used to avoid deadlock.
   *
   * <p>Usually, this call will complete normally if the time
   * expires, or abruptly with {@link InterruptedException}
   * if another thread called notify, but neither result
   * is guaranteed.
   *
   * <p>The waiting period is only *roughly* the amount of time
   * you requested.  It cannot be exact because of the overhead
   * of the call itself.  Most Virtual Machiness treat the
   * argument as a lower limit on the time spent waiting, but
   * even that is not guaranteed.  Besides, some other thread
   * may hold the lock on the object when the time expires, so
   * the current thread may still have to wait to reobtain the
   * lock.
   *
   * @param ms the minimum number of milliseconds to wait (1000
   *        milliseconds = 1 second), or 0 for an indefinite wait
   * @throws IllegalArgumentException if ms &lt; 0
   * @throws IllegalMonitorStateException if this Thread
   *         does not own a lock on this Object
   * @throws InterruptedException if some other Thread
   *         interrupts this Thread
   * @see #notify()
   * @see #notifyAll()
   * @see #wait()
   * @see #wait(long, int)
   * @see Thread
   */
  public final void wait(long ms)
    throws IllegalMonitorStateException, InterruptedException
  {
    wait(ms, 0);
  }

  /**
   * Waits a specified amount of time (or indefinitely if
   * the time specified is 0) for someone to call notify()
   * or notifyAll() on this Object, waking up this Thread.
   *
   * <p>The Thread that calls wait must have a lock on this Object,
   * obtained by a <code>synchronized</code> method or statement.
   * After calling wait, the thread loses the lock on this
   * object until the method completes (abruptly or normally),
   * at which time it regains the lock.  All locks held on
   * other objects remain in force, even though the thread is
   * inactive. Therefore, caution must be used to avoid deadlock.
   *
   * <p>Usually, this call will complete normally if the time
   * expires, or abruptly with {@link InterruptedException}
   * if another thread called notify, but neither result
   * is guaranteed.
   *
   * <p>The waiting period is nowhere near as precise as
   * nanoseconds; considering that even wait(int) is inaccurate,
   * how much can you expect?  But on supporting
   * implementations, this offers somewhat more granularity
   * than milliseconds.
   *
   * @param ms the number of milliseconds to wait (1,000
   *        milliseconds = 1 second)
   * @param ns the number of nanoseconds to wait over and
   *        above ms (1,000,000 nanoseconds = 1 millisecond)
   * @throws IllegalArgumentException if ms &lt; 0 or ns is not
   *         in the range 0 to 999,999
   * @throws IllegalMonitorStateException if this Thread
   *         does not own a lock on this Object
   * @throws InterruptedException if some other Thread
   *         interrupts this Thread
   * @see #notify()
   * @see #notifyAll()
   * @see #wait()
   * @see #wait(long)
   * @see Thread
   */
  public final void wait(long ms, int ns)
    throws IllegalMonitorStateException, InterruptedException
  {
    if (ms < 0 || ns < 0 || ns > 999999)
      throw new IllegalArgumentException("argument out of range");
    VMObject.wait(this, ms, ns);
  }
} // class Object