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What is Garbage collector in java and how it works?

Java is a language with automatic memory management. This was controlled by Garbage collector .Garbage collection is a process of marking unrefereed objects or unused object and removing them and making memory occupied by them available  to other new requirement. Unused objects ate those which are no more needed by the java application and do not contain any reference from application.

According to JDK 7, there are 5 GC types.

1.Serial GC
2.Parallel GC
3.Parallel Old GC (Parallel Compacting GC)
4.Concurrent Mark & Sweep GC  (or "CMS")
5.Garbage First (G1) GC

Different JVM uses different algorithms for Garbage collection some are :-

Marking and Sweeping Away Garbage

1.The algorithm traverses all object references, starting with the GC roots, and marks every object found as alive.
2.All of the heap memory that is not occupied by marked objects is reclaimed. It is simply marked as free, essentially swept free of unused objects

So instead of finding unused objects it finds the used objects and removes the all thing in left part of memory.

But the logical memory leaks cannot be determines by any software or any tools used for leak detection . What at maximum level they can do is they can mark the suspicious object and can suggest that they may be the culprit for memory leak.  

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