Object is the root of the class hierarchy.
* Every class has Object as a superclass. All objects,
* including arrays, implement the methods of this class.
*
* @author unascribed
* @version 1.67, 02/03/04
* @see java.lang.Class
* @since JDK1.0
*/
public class Object {
/**
* Returns the runtime class of an object. That Class
* object is the object that is locked by static synchronized
* methods of the represented class.
*
* @return The java.lang.Class object that represents
* the runtime class of the object. The result is of type
* {@code Class} where X is the
* static type of the expression on which
* getClass is called.
*/
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
* java.util.Hashtable.
*
* The general contract of hashCode is:
*
hashCode method on each of
* the two objects must produce the same integer result.
* * As much as is reasonably practical, the hashCode method defined by * class 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.util.Hashtable */ public native int hashCode(); /** * Indicates whether some other object is "equal to" this one. *
* The equals method implements an equivalence relation
* on non-null object references:
*
x, x.equals(x) should return
* true.
* x and y, x.equals(y)
* should return true if and only if
* y.equals(x) returns true.
* x, y, and z, if
* x.equals(y) returns true and
* y.equals(z) returns true, then
* x.equals(z) should return true.
* x and y, multiple invocations of
* x.equals(y) consistently return true
* or consistently return false, provided no
* information used in equals comparisons on the
* objects is modified.
* x,
* x.equals(null) should return false.
*
* The equals method for class Object implements
* the most discriminating possible equivalence relation on objects;
* that is, for any non-null reference values x and
* y, this method returns true if and only
* if x and y refer to the same object
* (x == y has the value true).
*
* Note that it is generally necessary to override the hashCode
* method whenever this method is overridden, so as to maintain the
* general contract for the hashCode method, which states
* that equal objects must have equal hash codes.
*
* @param obj the reference object with which to compare.
* @return true if this object is the same as the obj
* argument; false otherwise.
* @see #hashCode()
* @see java.util.Hashtable
*/
public boolean equals(Object obj) {
bi04t002a.instrInvoke(bi04t002a.INSTR_EQUALS);
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 x, the expression:
*
*
* x.clone() != x
* will be true, and that the expression:
*
*
* x.clone().getClass() == x.getClass()
* will be true, but these are not absolute requirements.
* While it is typically the case that:
*
*
* x.clone().equals(x)
* will be true, this is not an absolute requirement.
* * By convention, the returned object should be obtained by calling * super.clone. If a class and all of its superclasses (except * Object) obey this convention, it will be the case that * 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 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 super.clone * need to be modified. *
* The method clone for class Object performs a * specific cloning operation. First, if the class of this object does * not implement the interface Cloneable, then a * CloneNotSupportedException is thrown. Note that all arrays * are considered to implement the interface Cloneable. * 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 Object does not itself implement the interface
* Cloneable, so calling the clone method on an object
* whose class is 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 Cloneable interface. Subclasses
* that override the 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
* 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 toString method for class Object
* returns a string consisting of the name of the class of which the
* object is an instance, the at-sign character `@', 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:
*
*
* getClass().getName() + '@' + Integer.toHexString(hashCode())
*
*
* @return a string representation of the object.
*/
public String toString() {
bi04t002a.instrInvoke(bi04t002a.INSTR_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 wait methods.
* * 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: *
synchronized statement
* that synchronizes on the object.
* Class, by executing a
* synchronized static method of that class.
*
* 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
* 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 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 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 * {@link java.lang.Thread#interrupt() interrupted} by another thread * while it is waiting, then an InterruptedException is thrown. * This exception is not thrown until the lock status of this object has * been restored as described above. *
* Note that the 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 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 another 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 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 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, * wait(0, 0) means the same thing as 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: *
notify method
* or the notifyAll method.
* timeout
* milliseconds plus nanos nanoseconds arguments, has
* elapsed.
* * 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 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 another 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 {
bi04t002a.instrInvoke(bi04t002a.INSTR_WAIT_JI);
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 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 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 notify method or the
* 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 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 another 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 {
bi04t002a.instrInvoke(bi04t002a.INSTR_WAIT);
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 finalize method to dispose of
* system resources or to perform other cleanup.
* * The general contract of 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 finalize method may take any action, including * making this object available again to other threads; the usual purpose * of 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 finalize method of class Object performs no * special action; it simply returns normally. Subclasses of * Object may override this definition. *
* The Java programming language does not guarantee which thread will * invoke the 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 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 finalize method is never invoked more than once by a Java * virtual machine for any given object. *
* Any exception thrown by the finalize method causes
* the finalization of this object to be halted, but is otherwise
* ignored.
*
* @throws Throwable the Exception raised by this method
*/
protected void finalize() throws Throwable { }
}