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Class Object  view Object download


public abstract class Object
extends java.lang.Object


$Id:,v 1.8 2003/05/12 10:04:53 joewhaley Exp $

Constructor Summary
Method Summary
 java.lang.Class _getClass()
 void _notify()
 void _notifyAll()
 void _wait(long timeout)
protected  java.lang.Object clone()
          This method may be called to create a new copy of the Object.
 int hashCode()
          Get a value that represents this Object, as uniquely as possible within the confines of an int.
private static void registerNatives()
Methods inherited from class java.lang.Object
equals, finalize, getClass, notify, notifyAll, toString, wait, wait, wait

Constructor Detail


public Object()
Method Detail


private static void registerNatives()


public final java.lang.Class _getClass()


public int hashCode()
Description copied from class: java.lang.Object
Get a value that represents this Object, as uniquely as possible within the confines of an int.

There are some requirements on this method which subclasses must follow:

  • Semantic equality implies identical hashcodes. In other words, if a.equals(b) is true, then a.hashCode() == b.hashCode() must be as well. However, the reverse is not necessarily true, and two objects may have the same hashcode without being equal.
  • It must be consistent. Whichever value o.hashCode() returns on the first invocation must be the value returned on all later invocations as long as the object exists. Notice, however, that the result of hashCode may change between separate executions of a Virtual Machine, because it is not invoked on the same object.

Notice that since hashCode is used in java.util.Hashtable and other hashing classes, a poor implementation will degrade the performance of hashing (so don't blindly implement it as returning a constant!). Also, if calculating the hash is time-consuming, a class may consider caching the results.

The default implementation returns System.identityHashCode(this)


protected java.lang.Object clone()
                          throws java.lang.CloneNotSupportedException
Description copied from class: java.lang.Object
This method may be called to create a new copy of the Object. The typical behavior is as follows:
  • o == o.clone() is false
  • o.getClass() == o.clone().getClass() is true
  • o.equals(o) is true

However, these are not strict requirements, and may be violated if necessary. Of the three requirements, the last is the most commonly violated, particularly if the subclass does not override Object.equals(Object)>Object.equals(Object) 55 .

If the Object you call clone() on does not implement java.lang.Cloneable (which is a placeholder interface), then a CloneNotSupportedException is thrown. Notice that Object does not implement Cloneable; this method exists as a convenience for subclasses that do.

Object's implementation of clone allocates space for the new Object using the correct class, without calling any constructors, and then fills in all of the new field values with the old field values. Thus, it is a shallow copy. However, subclasses are permitted to make a deep copy.

All array types implement Cloneable, and override this method as follows (it should never fail):

 public Object clone()
   catch (CloneNotSupportedException e)
       throw new InternalError(e.getMessage());


public final void _notify()


public final void _notifyAll()


public final void _wait(long timeout)
                 throws java.lang.InterruptedException