| /* |
| * Copyright (c) 1994, 2010, 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; |
| |
| /** |
| * 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 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 Class Literals, section 15.8.2 of |
| * <cite>The Java™ Language Specification</cite>. |
| */ |
| public final native Class<?> getClass(); |
| |
| /** |
| * 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 java.lang.Object#equals(java.lang.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<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.lang.System#identityHashCode |
| */ |
| public native int hashCode(); |
| |
| /** |
| * 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. |
| * @exception 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 java.lang.Cloneable |
| */ |
| protected native Object clone() throws CloneNotSupportedException; |
| |
| /** |
| * 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. |
| * |
| * @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} 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. |
| * |
| * @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 {@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 (<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 |
| * {@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. |
| * @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} 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 (<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} 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 {@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 (<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} 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} 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<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 {@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 |
| */ |
| protected void finalize() throws Throwable { } |
| } |
