This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
A class can not be called "tightly encapsulated" unless which of the following is true? a. The class is declared final. b. All local variables are declared private. c. All method parameters are declared final. d. No method returns a reference to any object that is referenced by an internal data member. e. None of the above Answer : E. THe explanation is "However, the methods of a tightly encapsulated class may return a reference to an immutable object or a reference to a copy or clone of an internal object.". I don't quite understand to this sentence. What is "a reference to a copy or clone of an internal object"? And reference to an immutable object, does it mean to a String object? Thanks David
David, The following code demonstrates what can happen if you allow an object to return a reference to an internal object that is not immutable.
The program output is as follows. ABC ABCXYZ That problem can be avoided if the getIt method returns a reference to a copy of the StringBuffer instance rather than a reference to the same StringBuffer instance that is a member of class A.
Dan Chisholm<br />SCJP 1.4<br /> <br /><a href="http://www.danchisholm.net/" target="_blank" rel="nofollow">Try my mock exam.</a>
Joined: Dec 26, 2003
Hi Dan, Thanks for the reply. I am now understand ... Thanks