Avoid performing a deep copy if a shallow copy is all you require. For an object that contains pointers to other objects, a shallow copy copies only the pointers and not the objects to which they point. The result is two objects that point to the same contained object. A deep copy copies the pointers and the objects they point to, as well as any pointers or objects contained within that object, and so on.
(C) Copyright IBM Corporation 1992, 2005. All Rights Reserved.