--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/java/lang/Object.java Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,553 @@
+/*
+ * Copyright 1994-2006 Sun Microsystems, Inc. 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. Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+package java.lang;
+
+/**
+ * Class <code>Object</code> is the root of the class hierarchy.
+ * Every class has <code>Object</code> as a superclass. All objects,
+ * including arrays, implement the methods of this class.
+ *
+ * @author unascribed
+ * @see java.lang.Class
+ * @since JDK1.0
+ */
+public class Object {
+
+ private static native void registerNatives();
+ static {
+ registerNatives();
+ }
+
+ /**
+ * 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.
+ * @see <a href="http://java.sun.com/docs/books/jls/">The Java
+ * Language Specification, Third Edition (15.8.2 Class
+ * Literals)</a>
+ */
+ public final native Class<?> getClass();
+
+ /**
+ * Returns a hash code value for the object. This method is
+ * supported for the benefit of hashtables such as those provided by
+ * <code>java.util.Hashtable</code>.
+ * <p>
+ * The general contract of <code>hashCode</code> is:
+ * <ul>
+ * <li>Whenever it is invoked on the same object more than once during
+ * an execution of a Java application, the <tt>hashCode</tt> method
+ * must consistently return the same integer, provided no information
+ * used in <tt>equals</tt> 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 <tt>equals(Object)</tt>
+ * method, then calling the <code>hashCode</code> 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 java.lang.Object#equals(java.lang.Object)}
+ * method, then calling the <tt>hashCode</tt> 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 hashtables.
+ * </ul>
+ * <p>
+ * As much as is reasonably practical, the hashCode method defined by
+ * class <tt>Object</tt> 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<font size="-2"><sup>TM</sup></font> programming language.)
+ *
+ * @return a hash code value for this object.
+ * @see java.lang.Object#equals(java.lang.Object)
+ * @see java.util.Hashtable
+ */
+ public native int hashCode();
+
+ /**
+ * Indicates whether some other object is "equal to" this one.
+ * <p>
+ * The <code>equals</code> 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>, <code>x.equals(x)</code> should return
+ * <code>true</code>.
+ * <li>It is <i>symmetric</i>: for any non-null reference values
+ * <code>x</code> and <code>y</code>, <code>x.equals(y)</code>
+ * should return <code>true</code> if and only if
+ * <code>y.equals(x)</code> returns <code>true</code>.
+ * <li>It is <i>transitive</i>: for any non-null reference values
+ * <code>x</code>, <code>y</code>, and <code>z</code>, if
+ * <code>x.equals(y)</code> returns <code>true</code> and
+ * <code>y.equals(z)</code> returns <code>true</code>, then
+ * <code>x.equals(z)</code> should return <code>true</code>.
+ * <li>It is <i>consistent</i>: for any non-null reference values
+ * <code>x</code> and <code>y</code>, multiple invocations of
+ * <tt>x.equals(y)</tt> consistently return <code>true</code>
+ * or consistently return <code>false</code>, provided no
+ * information used in <code>equals</code> comparisons on the
+ * objects is modified.
+ * <li>For any non-null reference value <code>x</code>,
+ * <code>x.equals(null)</code> should return <code>false</code>.
+ * </ul>
+ * <p>
+ * The <tt>equals</tt> method for class <code>Object</code> implements
+ * the most discriminating possible equivalence relation on objects;
+ * that is, for any non-null reference values <code>x</code> and
+ * <code>y</code>, this method returns <code>true</code> if and only
+ * if <code>x</code> and <code>y</code> refer to the same object
+ * (<code>x == y</code> has the value <code>true</code>).
+ * <p>
+ * Note that it is generally necessary to override the <tt>hashCode</tt>
+ * method whenever this method is overridden, so as to maintain the
+ * general contract for the <tt>hashCode</tt> method, which states
+ * that equal objects must have equal hash codes.
+ *
+ * @param obj the reference object with which to compare.
+ * @return <code>true</code> if this object is the same as the obj
+ * argument; <code>false</code> otherwise.
+ * @see #hashCode()
+ * @see java.util.Hashtable
+ */
+ 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 <tt>x</tt>, 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 <tt>true</tt>, but these are not absolute requirements.
+ * While it is typically the case that:
+ * <blockquote>
+ * <pre>
+ * x.clone().equals(x)</pre></blockquote>
+ * will be <tt>true</tt>, this is not an absolute requirement.
+ * <p>
+ * By convention, the returned object should be obtained by calling
+ * <tt>super.clone</tt>. If a class and all of its superclasses (except
+ * <tt>Object</tt>) obey this convention, it will be the case that
+ * <tt>x.clone().getClass() == x.getClass()</tt>.
+ * <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 <tt>super.clone</tt> 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 <tt>super.clone</tt>
+ * need to be modified.
+ * <p>
+ * The method <tt>clone</tt> for class <tt>Object</tt> performs a
+ * specific cloning operation. First, if the class of this object does
+ * not implement the interface <tt>Cloneable</tt>, then a
+ * <tt>CloneNotSupportedException</tt> is thrown. Note that all arrays
+ * are considered to implement the interface <tt>Cloneable</tt>.
+ * 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 <tt>Object</tt> does not itself implement the interface
+ * <tt>Cloneable</tt>, so calling the <tt>clone</tt> method on an object
+ * whose class is <tt>Object</tt> will result in throwing an
+ * exception at run time.
+ *
+ * @return a clone of this instance.
+ * @exception CloneNotSupportedException if the object's class does not
+ * support the <code>Cloneable</code> interface. Subclasses
+ * that override the <code>clone</code> method can also
+ * throw this exception to indicate that an instance cannot
+ * be cloned.
+ * @see java.lang.Cloneable
+ */
+ protected native Object clone() throws CloneNotSupportedException;
+
+ /**
+ * Returns a string representation of the object. In general, the
+ * <code>toString</code> 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</code> method for class <code>Object</code>
+ * returns a string consisting of the name of the class of which the
+ * object is an instance, the at-sign character `<code>@</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</code> 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</code> statement
+ * that synchronizes on the object.
+ * <li>For objects of type <code>Class,</code> by executing a
+ * synchronized static method of that class.
+ * </ul>
+ * <p>
+ * Only one thread at a time can own an object's monitor.
+ *
+ * @exception IllegalMonitorStateException if the current thread is not
+ * the owner of this object's monitor.
+ * @see java.lang.Object#notifyAll()
+ * @see java.lang.Object#wait()
+ */
+ 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</code> 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</code> method for a
+ * description of the ways in which a thread can become the owner of
+ * a monitor.
+ *
+ * @exception IllegalMonitorStateException if the current thread is not
+ * the owner of this object's monitor.
+ * @see java.lang.Object#notify()
+ * @see java.lang.Object#wait()
+ */
+ public final native void notifyAll();
+
+ /**
+ * Causes the current thread to wait until either another thread invokes the
+ * {@link java.lang.Object#notify()} method or the
+ * {@link java.lang.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 <tt>notify</tt> 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 <tt>notifyAll</tt> 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
+ * <tt>timeout</tt> 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 <tt>wait</tt>
+ * method was invoked. Thread <var>T</var> then returns from the
+ * invocation of the <tt>wait</tt> method. Thus, on return from the
+ * <tt>wait</tt> method, the synchronization state of the object and of
+ * thread <tt>T</tt> is exactly as it was when the <tt>wait</tt> 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 (<condition does not hold>)
+ * 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 java.lang.Thread#interrupt()
+ * interrupted} by any thread before or while it is waiting, then an
+ * <tt>InterruptedException</tt> is thrown. This exception is not
+ * thrown until the lock status of this object has been restored as
+ * described above.
+ *
+ * <p>
+ * Note that the <tt>wait</tt> 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</code> 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.
+ * @exception IllegalArgumentException if the value of timeout is
+ * negative.
+ * @exception IllegalMonitorStateException if the current thread is not
+ * the owner of the object's monitor.
+ * @exception 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 java.lang.Object#notify()
+ * @see java.lang.Object#notifyAll()
+ */
+ public final native void wait(long timeout) throws InterruptedException;
+
+ /**
+ * Causes the current thread to wait until another thread invokes the
+ * {@link java.lang.Object#notify()} method or the
+ * {@link java.lang.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</code> 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,
+ * <tt>wait(0, 0)</tt> means the same thing as <tt>wait(0)</tt>.
+ * <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</code> method
+ * or the <code>notifyAll</code> method.
+ * <li>The timeout period, specified by <code>timeout</code>
+ * milliseconds plus <code>nanos</code> 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 (<condition does not hold>)
+ * 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</code> 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.
+ * @exception IllegalArgumentException if the value of timeout is
+ * negative or the value of nanos is
+ * not in the range 0-999999.
+ * @exception IllegalMonitorStateException if the current thread is not
+ * the owner of this object's monitor.
+ * @exception 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.
+ */
+ 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 >= 500000 || (nanos != 0 && timeout == 0)) {
+ timeout++;
+ }
+
+ wait(timeout);
+ }
+
+ /**
+ * Causes the current thread to wait until another thread invokes the
+ * {@link java.lang.Object#notify()} method or the
+ * {@link java.lang.Object#notifyAll()} method for this object.
+ * In other words, this method behaves exactly as if it simply
+ * performs the call <tt>wait(0)</tt>.
+ * <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</code> method or the
+ * <code>notifyAll</code> 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 (<condition does not hold>)
+ * 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</code> method for a
+ * description of the ways in which a thread can become the owner of
+ * a monitor.
+ *
+ * @exception IllegalMonitorStateException if the current thread is not
+ * the owner of the object's monitor.
+ * @exception 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 java.lang.Object#notify()
+ * @see java.lang.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</code> method to dispose of
+ * system resources or to perform other cleanup.
+ * <p>
+ * The general contract of <tt>finalize</tt> is that it is invoked
+ * if and when the Java<font size="-2"><sup>TM</sup></font> 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 <tt>finalize</tt> method may take any action, including
+ * making this object available again to other threads; the usual purpose
+ * of <tt>finalize</tt>, 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 <tt>finalize</tt> method of class <tt>Object</tt> performs no
+ * special action; it simply returns normally. Subclasses of
+ * <tt>Object</tt> may override this definition.
+ * <p>
+ * The Java programming language does not guarantee which thread will
+ * invoke the <tt>finalize</tt> 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 <tt>finalize</tt> 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 <tt>finalize</tt> method is never invoked more than once by a Java
+ * virtual machine for any given object.
+ * <p>
+ * Any exception thrown by the <code>finalize</code> method causes
+ * the finalization of this object to be halted, but is otherwise
+ * ignored.
+ *
+ * @throws Throwable the <code>Exception</code> raised by this method
+ */
+ protected void finalize() throws Throwable { }
+}