Mark and Sweep

[Pravin Panicker]

Hi EveryBody,
Does java use a mark and sweep algorithm for Garbage Collection?
Since the Garbage Collector calls finalize on unreferenced objects and collects them only on the subsequent round(s) ,is this not mark 'n sweep ?
Thanks and Regards,
-- Pravin Panicker

[bill bozeman]

Depends on the Java implentation. Some may use it, and some may not. So for questions like this, your answer will be maybe they do, maybe they don't.
Bill

[Val Dra]

I'd say it does when a minimum clean up is required. It uses a few algorithms at least that's what Bruce Eckel is saying. When the clean up is minimum and garbage collector runs it chooses that algorithm for fast clean up.

[Junaid Bhatra]

Garbage collection algorithms is a very well-studied area. Like Bill said, which garbage-collection algorithm a JVM uses is upto the implementor of the JVM. The JLS only says that unreferenced objects are eligible for garbage-collection. It is not even compulsory for a JVM to have a garbage collector!
There are basically 2 approaches: reference counting, and tracing algorithms. The earliest implementations of the JVM by Sun used reference counting, but it is no longer used. The current JVM's probably use a sophisticated tracing algorithm. Mark & sweep is the simplest form of a tracing gc algorithm. Also the garbage-collector will have certain techniques for combating heap fragmentation too.

Originally posted by Pravin Panicker:
Hi EveryBody,
Does java use a mark and sweep algorithm for Garbage Collection?
Since the Garbage Collector calls finalize on unreferenced objects and collects them only on the subsequent round(s) ,is this not mark 'n sweep ?
Thanks and Regards,
-- Pravin Panicker