The actual result type is {@code Class} jaroslav@49: * where {@code |X|} is the erasure of the static type of the jaroslav@49: * expression on which {@code getClass} is called. For jaroslav@49: * example, no cast is required in this code fragment:
jaroslav@49: * jaroslav@49: *
jaroslav@49: * {@code Number n = 0; }
jaroslav@49: * {@code Class c = n.getClass(); }
jaroslav@49: *
jaroslav@49: * The general contract of {@code hashCode} is: jaroslav@49: *
jaroslav@49: * As much as is reasonably practical, the hashCode method defined by jaroslav@49: * class {@code Object} does return distinct integers for distinct jaroslav@49: * objects. (This is typically implemented by converting the internal jaroslav@49: * address of the object into an integer, but this implementation jaroslav@49: * technique is not required by the jaroslav@49: * JavaTM programming language.) jaroslav@49: * jaroslav@49: * @return a hash code value for this object. jaroslav@49: * @see java.lang.Object#equals(java.lang.Object) jaroslav@49: * @see java.lang.System#identityHashCode jaroslav@49: */ jaroslav@49: public native int hashCode(); jaroslav@49: jaroslav@49: /** jaroslav@49: * Indicates whether some other object is "equal to" this one. jaroslav@49: *
jaroslav@49: * The {@code equals} method implements an equivalence relation jaroslav@49: * on non-null object references: jaroslav@49: *
jaroslav@49: * The {@code equals} method for class {@code Object} implements jaroslav@49: * the most discriminating possible equivalence relation on objects; jaroslav@49: * that is, for any non-null reference values {@code x} and jaroslav@49: * {@code y}, this method returns {@code true} if and only jaroslav@49: * if {@code x} and {@code y} refer to the same object jaroslav@49: * ({@code x == y} has the value {@code true}). jaroslav@49: *
jaroslav@49: * Note that it is generally necessary to override the {@code hashCode} jaroslav@49: * method whenever this method is overridden, so as to maintain the jaroslav@49: * general contract for the {@code hashCode} method, which states jaroslav@49: * that equal objects must have equal hash codes. jaroslav@49: * jaroslav@49: * @param obj the reference object with which to compare. jaroslav@49: * @return {@code true} if this object is the same as the obj jaroslav@49: * argument; {@code false} otherwise. jaroslav@49: * @see #hashCode() jaroslav@49: * @see java.util.HashMap jaroslav@49: */ jaroslav@49: public boolean equals(Object obj) { jaroslav@49: return (this == obj); jaroslav@49: } jaroslav@49: jaroslav@49: /** jaroslav@49: * Creates and returns a copy of this object. The precise meaning jaroslav@49: * of "copy" may depend on the class of the object. The general jaroslav@49: * intent is that, for any object {@code x}, the expression: jaroslav@49: *
jaroslav@49: *jaroslav@49: * will be true, and that the expression: jaroslav@49: *jaroslav@49: * x.clone() != x
jaroslav@49: *jaroslav@49: * will be {@code true}, but these are not absolute requirements. jaroslav@49: * While it is typically the case that: jaroslav@49: *jaroslav@49: * x.clone().getClass() == x.getClass()
jaroslav@49: *jaroslav@49: * will be {@code true}, this is not an absolute requirement. jaroslav@49: *jaroslav@49: * x.clone().equals(x)
jaroslav@49: * By convention, the returned object should be obtained by calling jaroslav@49: * {@code super.clone}. If a class and all of its superclasses (except jaroslav@49: * {@code Object}) obey this convention, it will be the case that jaroslav@49: * {@code x.clone().getClass() == x.getClass()}. jaroslav@49: *
jaroslav@49: * By convention, the object returned by this method should be independent jaroslav@49: * of this object (which is being cloned). To achieve this independence, jaroslav@49: * it may be necessary to modify one or more fields of the object returned jaroslav@49: * by {@code super.clone} before returning it. Typically, this means jaroslav@49: * copying any mutable objects that comprise the internal "deep structure" jaroslav@49: * of the object being cloned and replacing the references to these jaroslav@49: * objects with references to the copies. If a class contains only jaroslav@49: * primitive fields or references to immutable objects, then it is usually jaroslav@49: * the case that no fields in the object returned by {@code super.clone} jaroslav@49: * need to be modified. jaroslav@49: *
jaroslav@49: * The method {@code clone} for class {@code Object} performs a jaroslav@49: * specific cloning operation. First, if the class of this object does jaroslav@49: * not implement the interface {@code Cloneable}, then a jaroslav@49: * {@code CloneNotSupportedException} is thrown. Note that all arrays jaroslav@49: * are considered to implement the interface {@code Cloneable} and that jaroslav@49: * the return type of the {@code clone} method of an array type {@code T[]} jaroslav@49: * is {@code T[]} where T is any reference or primitive type. jaroslav@49: * Otherwise, this method creates a new instance of the class of this jaroslav@49: * object and initializes all its fields with exactly the contents of jaroslav@49: * the corresponding fields of this object, as if by assignment; the jaroslav@49: * contents of the fields are not themselves cloned. Thus, this method jaroslav@49: * performs a "shallow copy" of this object, not a "deep copy" operation. jaroslav@49: *
jaroslav@49: * The class {@code Object} does not itself implement the interface jaroslav@49: * {@code Cloneable}, so calling the {@code clone} method on an object jaroslav@49: * whose class is {@code Object} will result in throwing an jaroslav@49: * exception at run time. jaroslav@49: * jaroslav@49: * @return a clone of this instance. jaroslav@49: * @exception CloneNotSupportedException if the object's class does not jaroslav@49: * support the {@code Cloneable} interface. Subclasses jaroslav@49: * that override the {@code clone} method can also jaroslav@49: * throw this exception to indicate that an instance cannot jaroslav@49: * be cloned. jaroslav@49: * @see java.lang.Cloneable jaroslav@49: */ jaroslav@49: protected native Object clone() throws CloneNotSupportedException; jaroslav@49: jaroslav@49: /** jaroslav@49: * Returns a string representation of the object. In general, the jaroslav@49: * {@code toString} method returns a string that jaroslav@49: * "textually represents" this object. The result should jaroslav@49: * be a concise but informative representation that is easy for a jaroslav@49: * person to read. jaroslav@49: * It is recommended that all subclasses override this method. jaroslav@49: *
jaroslav@49: * The {@code toString} method for class {@code Object} jaroslav@49: * returns a string consisting of the name of the class of which the jaroslav@49: * object is an instance, the at-sign character `{@code @}', and jaroslav@49: * the unsigned hexadecimal representation of the hash code of the jaroslav@49: * object. In other words, this method returns a string equal to the jaroslav@49: * value of: jaroslav@49: *
jaroslav@49: *jaroslav@49: * jaroslav@49: * @return a string representation of the object. jaroslav@49: */ jaroslav@49: public String toString() { jaroslav@49: return getClass().getName() + "@" + Integer.toHexString(hashCode()); jaroslav@49: } jaroslav@49: jaroslav@49: /** jaroslav@49: * Wakes up a single thread that is waiting on this object's jaroslav@49: * monitor. If any threads are waiting on this object, one of them jaroslav@49: * is chosen to be awakened. The choice is arbitrary and occurs at jaroslav@49: * the discretion of the implementation. A thread waits on an object's jaroslav@49: * monitor by calling one of the {@code wait} methods. jaroslav@49: *jaroslav@49: * getClass().getName() + '@' + Integer.toHexString(hashCode()) jaroslav@49: *
jaroslav@49: * The awakened thread will not be able to proceed until the current jaroslav@49: * thread relinquishes the lock on this object. The awakened thread will jaroslav@49: * compete in the usual manner with any other threads that might be jaroslav@49: * actively competing to synchronize on this object; for example, the jaroslav@49: * awakened thread enjoys no reliable privilege or disadvantage in being jaroslav@49: * the next thread to lock this object. jaroslav@49: *
jaroslav@49: * This method should only be called by a thread that is the owner jaroslav@49: * of this object's monitor. A thread becomes the owner of the jaroslav@49: * object's monitor in one of three ways: jaroslav@49: *
jaroslav@49: * Only one thread at a time can own an object's monitor. jaroslav@49: * jaroslav@49: * @exception IllegalMonitorStateException if the current thread is not jaroslav@49: * the owner of this object's monitor. jaroslav@49: * @see java.lang.Object#notifyAll() jaroslav@49: * @see java.lang.Object#wait() jaroslav@49: */ jaroslav@49: public final native void notify(); jaroslav@49: jaroslav@49: /** jaroslav@49: * Wakes up all threads that are waiting on this object's monitor. A jaroslav@49: * thread waits on an object's monitor by calling one of the jaroslav@49: * {@code wait} methods. jaroslav@49: *
jaroslav@49: * The awakened threads will not be able to proceed until the current jaroslav@49: * thread relinquishes the lock on this object. The awakened threads jaroslav@49: * will compete in the usual manner with any other threads that might jaroslav@49: * be actively competing to synchronize on this object; for example, jaroslav@49: * the awakened threads enjoy no reliable privilege or disadvantage in jaroslav@49: * being the next thread to lock this object. jaroslav@49: *
jaroslav@49: * This method should only be called by a thread that is the owner jaroslav@49: * of this object's monitor. See the {@code notify} method for a jaroslav@49: * description of the ways in which a thread can become the owner of jaroslav@49: * a monitor. jaroslav@49: * jaroslav@49: * @exception IllegalMonitorStateException if the current thread is not jaroslav@49: * the owner of this object's monitor. jaroslav@49: * @see java.lang.Object#notify() jaroslav@49: * @see java.lang.Object#wait() jaroslav@49: */ jaroslav@49: public final native void notifyAll(); jaroslav@49: jaroslav@49: /** jaroslav@49: * Causes the current thread to wait until either another thread invokes the jaroslav@49: * {@link java.lang.Object#notify()} method or the jaroslav@49: * {@link java.lang.Object#notifyAll()} method for this object, or a jaroslav@49: * specified amount of time has elapsed. jaroslav@49: *
jaroslav@49: * The current thread must own this object's monitor. jaroslav@49: *
jaroslav@49: * This method causes the current thread (call it T) to jaroslav@49: * place itself in the wait set for this object and then to relinquish jaroslav@49: * any and all synchronization claims on this object. Thread T jaroslav@49: * becomes disabled for thread scheduling purposes and lies dormant jaroslav@49: * until one of four things happens: jaroslav@49: *
jaroslav@49: * A thread can also wake up without being notified, interrupted, or jaroslav@49: * timing out, a so-called spurious wakeup. While this will rarely jaroslav@49: * occur in practice, applications must guard against it by testing for jaroslav@49: * the condition that should have caused the thread to be awakened, and jaroslav@49: * continuing to wait if the condition is not satisfied. In other words, jaroslav@49: * waits should always occur in loops, like this one: jaroslav@49: *
jaroslav@49: * synchronized (obj) {
jaroslav@49: * while (<condition does not hold>)
jaroslav@49: * obj.wait(timeout);
jaroslav@49: * ... // Perform action appropriate to condition
jaroslav@49: * }
jaroslav@49: *
jaroslav@49: * (For more information on this topic, see Section 3.2.3 in Doug Lea's
jaroslav@49: * "Concurrent Programming in Java (Second Edition)" (Addison-Wesley,
jaroslav@49: * 2000), or Item 50 in Joshua Bloch's "Effective Java Programming
jaroslav@49: * Language Guide" (Addison-Wesley, 2001).
jaroslav@49: *
jaroslav@49: * If the current thread is {@linkplain java.lang.Thread#interrupt() jaroslav@49: * interrupted} by any thread before or while it is waiting, then an jaroslav@49: * {@code InterruptedException} is thrown. This exception is not jaroslav@49: * thrown until the lock status of this object has been restored as jaroslav@49: * described above. jaroslav@49: * jaroslav@49: *
jaroslav@49: * Note that the {@code wait} method, as it places the current thread jaroslav@49: * into the wait set for this object, unlocks only this object; any jaroslav@49: * other objects on which the current thread may be synchronized remain jaroslav@49: * locked while the thread waits. jaroslav@49: *
jaroslav@49: * This method should only be called by a thread that is the owner jaroslav@49: * of this object's monitor. See the {@code notify} method for a jaroslav@49: * description of the ways in which a thread can become the owner of jaroslav@49: * a monitor. jaroslav@49: * jaroslav@49: * @param timeout the maximum time to wait in milliseconds. jaroslav@49: * @exception IllegalArgumentException if the value of timeout is jaroslav@49: * negative. jaroslav@49: * @exception IllegalMonitorStateException if the current thread is not jaroslav@49: * the owner of the object's monitor. jaroslav@49: * @exception InterruptedException if any thread interrupted the jaroslav@49: * current thread before or while the current thread jaroslav@49: * was waiting for a notification. The interrupted jaroslav@49: * status of the current thread is cleared when jaroslav@49: * this exception is thrown. jaroslav@49: * @see java.lang.Object#notify() jaroslav@49: * @see java.lang.Object#notifyAll() jaroslav@49: */ jaroslav@49: public final native void wait(long timeout) throws InterruptedException; jaroslav@49: jaroslav@49: /** jaroslav@49: * Causes the current thread to wait until another thread invokes the jaroslav@49: * {@link java.lang.Object#notify()} method or the jaroslav@49: * {@link java.lang.Object#notifyAll()} method for this object, or jaroslav@49: * some other thread interrupts the current thread, or a certain jaroslav@49: * amount of real time has elapsed. jaroslav@49: *
jaroslav@49: * This method is similar to the {@code wait} method of one jaroslav@49: * argument, but it allows finer control over the amount of time to jaroslav@49: * wait for a notification before giving up. The amount of real time, jaroslav@49: * measured in nanoseconds, is given by: jaroslav@49: *
jaroslav@49: *jaroslav@49: *jaroslav@49: * 1000000*timeout+nanos
jaroslav@49: * In all other respects, this method does the same thing as the jaroslav@49: * method {@link #wait(long)} of one argument. In particular, jaroslav@49: * {@code wait(0, 0)} means the same thing as {@code wait(0)}. jaroslav@49: *
jaroslav@49: * The current thread must own this object's monitor. The thread jaroslav@49: * releases ownership of this monitor and waits until either of the jaroslav@49: * following two conditions has occurred: jaroslav@49: *
jaroslav@49: * The thread then waits until it can re-obtain ownership of the jaroslav@49: * monitor and resumes execution. jaroslav@49: *
jaroslav@49: * As in the one argument version, interrupts and spurious wakeups are jaroslav@49: * possible, and this method should always be used in a loop: jaroslav@49: *
jaroslav@49: * synchronized (obj) {
jaroslav@49: * while (<condition does not hold>)
jaroslav@49: * obj.wait(timeout, nanos);
jaroslav@49: * ... // Perform action appropriate to condition
jaroslav@49: * }
jaroslav@49: *
jaroslav@49: * This method should only be called by a thread that is the owner
jaroslav@49: * of this object's monitor. See the {@code notify} method for a
jaroslav@49: * description of the ways in which a thread can become the owner of
jaroslav@49: * a monitor.
jaroslav@49: *
jaroslav@49: * @param timeout the maximum time to wait in milliseconds.
jaroslav@49: * @param nanos additional time, in nanoseconds range
jaroslav@49: * 0-999999.
jaroslav@49: * @exception IllegalArgumentException if the value of timeout is
jaroslav@49: * negative or the value of nanos is
jaroslav@49: * not in the range 0-999999.
jaroslav@49: * @exception IllegalMonitorStateException if the current thread is not
jaroslav@49: * the owner of this object's monitor.
jaroslav@49: * @exception InterruptedException if any thread interrupted the
jaroslav@49: * current thread before or while the current thread
jaroslav@49: * was waiting for a notification. The interrupted
jaroslav@49: * status of the current thread is cleared when
jaroslav@49: * this exception is thrown.
jaroslav@49: */
jaroslav@49: public final void wait(long timeout, int nanos) throws InterruptedException {
jaroslav@49: if (timeout < 0) {
jaroslav@49: throw new IllegalArgumentException("timeout value is negative");
jaroslav@49: }
jaroslav@49:
jaroslav@49: if (nanos < 0 || nanos > 999999) {
jaroslav@49: throw new IllegalArgumentException(
jaroslav@49: "nanosecond timeout value out of range");
jaroslav@49: }
jaroslav@49:
jaroslav@49: if (nanos >= 500000 || (nanos != 0 && timeout == 0)) {
jaroslav@49: timeout++;
jaroslav@49: }
jaroslav@49:
jaroslav@49: wait(timeout);
jaroslav@49: }
jaroslav@49:
jaroslav@49: /**
jaroslav@49: * Causes the current thread to wait until another thread invokes the
jaroslav@49: * {@link java.lang.Object#notify()} method or the
jaroslav@49: * {@link java.lang.Object#notifyAll()} method for this object.
jaroslav@49: * In other words, this method behaves exactly as if it simply
jaroslav@49: * performs the call {@code wait(0)}.
jaroslav@49: * jaroslav@49: * The current thread must own this object's monitor. The thread jaroslav@49: * releases ownership of this monitor and waits until another thread jaroslav@49: * notifies threads waiting on this object's monitor to wake up jaroslav@49: * either through a call to the {@code notify} method or the jaroslav@49: * {@code notifyAll} method. The thread then waits until it can jaroslav@49: * re-obtain ownership of the monitor and resumes execution. jaroslav@49: *
jaroslav@49: * As in the one argument version, interrupts and spurious wakeups are jaroslav@49: * possible, and this method should always be used in a loop: jaroslav@49: *
jaroslav@49: * synchronized (obj) {
jaroslav@49: * while (<condition does not hold>)
jaroslav@49: * obj.wait();
jaroslav@49: * ... // Perform action appropriate to condition
jaroslav@49: * }
jaroslav@49: *
jaroslav@49: * This method should only be called by a thread that is the owner
jaroslav@49: * of this object's monitor. See the {@code notify} method for a
jaroslav@49: * description of the ways in which a thread can become the owner of
jaroslav@49: * a monitor.
jaroslav@49: *
jaroslav@49: * @exception IllegalMonitorStateException if the current thread is not
jaroslav@49: * the owner of the object's monitor.
jaroslav@49: * @exception InterruptedException if any thread interrupted the
jaroslav@49: * current thread before or while the current thread
jaroslav@49: * was waiting for a notification. The interrupted
jaroslav@49: * status of the current thread is cleared when
jaroslav@49: * this exception is thrown.
jaroslav@49: * @see java.lang.Object#notify()
jaroslav@49: * @see java.lang.Object#notifyAll()
jaroslav@49: */
jaroslav@49: public final void wait() throws InterruptedException {
jaroslav@49: wait(0);
jaroslav@49: }
jaroslav@49:
jaroslav@49: /**
jaroslav@49: * Called by the garbage collector on an object when garbage collection
jaroslav@49: * determines that there are no more references to the object.
jaroslav@49: * A subclass overrides the {@code finalize} method to dispose of
jaroslav@49: * system resources or to perform other cleanup.
jaroslav@49: * jaroslav@49: * The general contract of {@code finalize} is that it is invoked jaroslav@49: * if and when the JavaTM virtual jaroslav@49: * machine has determined that there is no longer any jaroslav@49: * means by which this object can be accessed by any thread that has jaroslav@49: * not yet died, except as a result of an action taken by the jaroslav@49: * finalization of some other object or class which is ready to be jaroslav@49: * finalized. The {@code finalize} method may take any action, including jaroslav@49: * making this object available again to other threads; the usual purpose jaroslav@49: * of {@code finalize}, however, is to perform cleanup actions before jaroslav@49: * the object is irrevocably discarded. For example, the finalize method jaroslav@49: * for an object that represents an input/output connection might perform jaroslav@49: * explicit I/O transactions to break the connection before the object is jaroslav@49: * permanently discarded. jaroslav@49: *
jaroslav@49: * The {@code finalize} method of class {@code Object} performs no jaroslav@49: * special action; it simply returns normally. Subclasses of jaroslav@49: * {@code Object} may override this definition. jaroslav@49: *
jaroslav@49: * The Java programming language does not guarantee which thread will jaroslav@49: * invoke the {@code finalize} method for any given object. It is jaroslav@49: * guaranteed, however, that the thread that invokes finalize will not jaroslav@49: * be holding any user-visible synchronization locks when finalize is jaroslav@49: * invoked. If an uncaught exception is thrown by the finalize method, jaroslav@49: * the exception is ignored and finalization of that object terminates. jaroslav@49: *
jaroslav@49: * After the {@code finalize} method has been invoked for an object, no jaroslav@49: * further action is taken until the Java virtual machine has again jaroslav@49: * determined that there is no longer any means by which this object can jaroslav@49: * be accessed by any thread that has not yet died, including possible jaroslav@49: * actions by other objects or classes which are ready to be finalized, jaroslav@49: * at which point the object may be discarded. jaroslav@49: *
jaroslav@49: * The {@code finalize} method is never invoked more than once by a Java jaroslav@49: * virtual machine for any given object. jaroslav@49: *
jaroslav@49: * Any exception thrown by the {@code finalize} method causes jaroslav@49: * the finalization of this object to be halted, but is otherwise jaroslav@49: * ignored. jaroslav@49: * jaroslav@49: * @throws Throwable the {@code Exception} raised by this method jaroslav@49: */ jaroslav@49: protected void finalize() throws Throwable { } jaroslav@49: }