Mughal's Mock Exam-Garbage Collection

[Betty Reynolds]

I got this wrong the first time I went through the exam because of the reason below, and the more I think about, the more I think this question is in error.

Which statements decribe guaranteed behavior of the garbage collection and
 finalization mechanisms? 
1) Objects are deleted when they can no longer be accessed through any reference.
2) The finalize() method will eventually be called on every object.
3) The finalize() method will never be called more than once on an object.
4) An object will not be garbage collected as long as it is possible for an active part
 of the program to access it through a reference.
5) The garbage collector will use a mark and sweep algorithm.

The answer given is c and d. "Very little is guaranteed about the behavior of the garbage collection and finalization mechanisms. The (c) and (d) statements are two of the things that are guaranteed."
Well nothing about the language can be guaranteed--almost anything is subject to change in the future. We can only base our answers on what is true now. Therefore, (e) is correct also.
The Java Tutorial states:

The Java platform has a garbage collector that periodically frees the memory used by objects that are no longer needed. The Java garbage collector is a mark-sweep garbage collector. A mark-sweep garbage collector scans dynamic memory areas for objects and marks those that are referenced. After all possible paths to objects are investigated, unmarked objects (unreferenced objects) are known to be garbage and are collected. (A more complete description of Java's garbage collection algorithm might be "a compacting, mark-sweep collector with some conservative scanning.")

Also, Peter van der Linden in Just Java 2 states "The current Java implementatin from Sun uses the "mark and sweep" garbage collection algorithm" (p. 297).

[This message has been edited by Betty Reynolds (edited April 10, 2000).]

[maha anna]

Betty,
Can you post the MockExam name and the qstn no. please?
Thank you.
regds
maha anna

[Betty Reynolds]

It's the mock exam associated with this book.
Mughal & Rassmussen's A Programmer's Guide to Java Certification
Sometimes referred to at this site as "Khalid's test."
I can't post the question #. It's different every time around because the questions get "shuffled" randomly before they are presented. In the book, which is good by the way, the question number is #30.

[This message has been edited by Betty Reynolds (edited April 10, 2000).]

[Anonymous]

as i understand it, gc implementation is not specified in the java specifications so an implementation is free to use whatever algorithm it wishes. the sun jdk uses the mark and sweep but other implementations of the jdk may use a different algorithm