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§1.12 Class Object

public  class  java.lang.Object
{
        // Constructors
    public Object();	§1.12.1

        // Methods
    protected Object clone();	§1.12.2
    public boolean equals(Object  obj);	§1.12.3
    protected void finalize();	§1.12.4
    public final Class getClass();	§1.12.5
    public int hashCode();	§1.12.6
    public final void notify();	§1.12.7
    public final void notifyAll();	§1.12.8
    public String toString();	§1.12.9
    public final void wait();	§1.12.10
    public final void wait(long  timeout);	§1.12.11
    public final void wait(long  timeout, int  nanos);	§1.12.12
}
Class Object is the root of the class hierarchy. Every class has Object as a superclass. parent. All objects, including arrays, implement the methods of this class.


Constructors

Object

public Object()
Allocates a new instance of class Object.

Methods

clone

protected Object clone() throws CloneNotSupportedException
The clone method of class Object creates a new object of the same class as this object. It then initializes each of the new object's fields by assigning it the same value as the corresponding field in this object. No constructor is called.
The clone method of class Object will only clone an object whose class indicates that it is willing for its instances to be cloned. A class indicates that its instances can be cloned by declaring that it implements the Cloneable (I-§1.22) interface.

Returns:
a clone of this instance.
Throws
OutOfMemoryError (I-§1.57)
If there is not enough memory.
Throws
CloneNotSupportedException (I-§1.29)
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.

equals

public boolean equals(Object obj)
Indicates whether some other object is "equal to" this one.
The equals method implements an equivalence relation:
The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any 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).
Parameters:
obj - the reference object with which to compare
Returns:
true if this object is the same as the obj argument; false otherwise.
See Also:
Hashtable (I-§3.4)
hashCode (§1.12.6).

finalize

protected void finalize() throws Throwable
The finalize method is 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 in order to dispose of system resources or to perform other cleanup.
Any exception thrown by the finalize method causes the finalization of this object to be halted, but is otherwise ignored.
The finalize method in Object does nothing.

getClass

public final Class getClass()
Determines the run-time class of an object.
Returns:
the object of type Class (I-§1.3) that represents the run-time class of the object.

hashCode

public int hashCode()
Calculates a hash code value for the object. This method is supported for the benefit of hash tables such as those provided by java.util.Hashtable (I-§3.4).


The general contract of hashCode is:
Returns:
a hash code value for this object.

notify

public final void notify()
Wakes up a single thread that is waiting on this object's monitor. A thread waits on an object's monitor by calling one of the wait methods (I-§1.12.10-§1.12.12).


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 only an object's monitor.
Throws
IllegalMonitorStateException (I-§1.33)
If the current thread is not the owner of this object's monitor.
See Also:
notifyAll (I-§1.12.8).

notifyAll

public final void notifyAll()
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 (I-§1.12.10-§1.12.12).


This method should only be called by a thread that is the owner of this object's monitor. See the notify method (I-§1.12.7) for a description of the ways in which a thread can become the owner of a monitor.

Throws
IllegalMonitorStateException (I-§1.33)
If the current thread is not the owner of this object's monitor.

toString

public String toString()
Creates 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.
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 object1.

Returns:
A string representation of the object.

wait

public final void wait() throws InterruptedException
Waits to be notified by another thread of a change in this object.
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 (I-§1.12.7) or the notifyAll method(I-§1.12.7). The thread then waits until it can re-obtain ownership of the monitor and resumes execution.


This method should only be called by a thread that is the owner of this object's monitor. See the notify method (I-§1.12.7) for a description of the ways in which a thread can become the owner of a monitor.

Throws
IllegalMonitorStateException (I-§1.33)
If the current thread is not the owner of the object's monitor.
Throws
InterruptedException (I-§1.37)
Another thread has interrupted this thread.

wait

public final void wait(long timeout) throws InterruptedException
Waits to be notified by another thread of a change in this object.
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
This method should only be called by a thread that is the owner of this object's monitor. See the notify method (I-§1.12.7) for a description of the ways in which a thread can become the owner of a monitor.

Parameters:
timeout - the maximum time to wait in milliseconds
Throws
IllegalMonitorStateException (I-§1.33)
If the current thread is not the owner of the object's monitor.
Throws
InterruptedException (I-§1.37)
Another thread has interrupted this thread.

wait

public final void wait(long timeout, int nanos) throws InterruptedException
Waits to be notified by another thread of a change in this object.
This method is similar to the wait method (I-§1.12.11) of one argument, but it allows finer control over the amount of time to wait for a notification before giving up.


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
This method should only be called by a thread that is the owner of this object's monitor. See the notify method (I-§1.12.7) for a description of the ways in which a thread can become the owner of a monitor.

Parameters:
timeout - the maximum time to wait in milliseconds
nano - additional time, in nanoseconds range 0-999999
Throws
IllegalMonitorStateException (I-§1.33)
If the current thread is not the owner of this object's monitor.
Throws
InterruptedException (I-§1.37)
Another thread has interrupted this thread.

1 In Java 1.0, the hexidecimal string printed after the `@' is based on the hash code value, but may not be the actual hash code value.

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Java API Document (HTML generated by dkramer on April 22, 1996)
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