The actual result type is {@code Class} + * where {@code |X|} is the erasure of the static type of the + * expression on which {@code getClass} is called. For + * example, no cast is required in this code fragment:
+ * + *
+ * {@code Number n = 0; }
+ * {@code Class c = n.getClass(); }
+ *
+ * The general contract of {@code hashCode} is: + *
+ * 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 + * JavaTM 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. + *
+ * The {@code equals} method implements an equivalence relation + * on non-null object references: + *
+ * 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}). + *
+ * 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: + *
+ *+ * will be true, and that the expression: + *+ * x.clone() != x
+ *+ * will be {@code true}, but these are not absolute requirements. + * While it is typically the case that: + *+ * x.clone().getClass() == x.getClass()
+ *+ * will be {@code true}, this is not an absolute requirement. + *+ * x.clone().equals(x)
+ * 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()}. + *
+ * 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. + *
+ * 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. + *
+ * 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. + *
+ * 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: + *
+ *+ * + * @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. + *+ * getClass().getName() + '@' + Integer.toHexString(hashCode()) + *
+ * 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. + *
+ * 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: + *
+ * 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. + *
+ * 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. + *
+ * 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. + *
+ * The current thread must own this object's monitor. + *
+ * This method causes the current thread (call it T) to + * place itself in the wait set for this object and then to relinquish + * any and all synchronization claims on this object. Thread T + * becomes disabled for thread scheduling purposes and lies dormant + * until one of four things happens: + *
+ * A thread can also wake up without being notified, interrupted, or + * timing out, a so-called spurious wakeup. 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: + *
+ * synchronized (obj) {
+ * while (<condition does not hold>)
+ * obj.wait(timeout);
+ * ... // Perform action appropriate to condition
+ * }
+ *
+ * (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).
+ *
+ * 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. + * + *
+ * 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. + *
+ * 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 interrupted + * status 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. + *
+ * 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: + *
+ *+ *+ * 1000000*timeout+nanos
+ * 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)}. + *
+ * 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: + *
+ * The thread then waits until it can re-obtain ownership of the + * monitor and resumes execution. + *
+ * As in the one argument version, interrupts and spurious wakeups are + * possible, and this method should always be used in a loop: + *
+ * synchronized (obj) {
+ * while (<condition does not hold>)
+ * obj.wait(timeout, nanos);
+ * ... // Perform action appropriate to condition
+ * }
+ *
+ * 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 interrupted
+ * status 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)}.
+ * + * 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. + *
+ * As in the one argument version, interrupts and spurious wakeups are + * possible, and this method should always be used in a loop: + *
+ * synchronized (obj) {
+ * while (<condition does not hold>)
+ * obj.wait();
+ * ... // Perform action appropriate to condition
+ * }
+ *
+ * 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 interrupted
+ * status 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.
+ * + * The general contract of {@code finalize} is that it is invoked + * if and when the JavaTM 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. + *
+ * The {@code finalize} method of class {@code Object} performs no + * special action; it simply returns normally. Subclasses of + * {@code Object} may override this definition. + *
+ * 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. + *
+ * 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. + *
+ * The {@code finalize} method is never invoked more than once by a Java + * virtual machine for any given object. + *
+ * 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 { } +}