Your question is not clear. I guess, you may be referring to "copying the state of an object to another object of the same Class type" . If that is the case, then there is a method called clone() in the Object Class that has to be overridden by the Class of the object in consideration.
First, if the class of this object does not implement the interface Cloneable, then a CloneNotSupportedException is thrown.
There are two kinds of cloning "Shallow Cloning" and "Deep Cloning".
Further reading is recommended at the following link.
http://www.java.sun.com/j2se/1.3/docs/api/java/lang/Object.html [ June 14, 2006: Message edited by: Ramasubbhu Allur Kuppusamy ]