system.gc

garbage collections will be handled by JVM itself means ,how does it know that the object is no longer needed by the prgm.
memory recycling ,if i use system.gc whether it's a worst programming style or optimized one.

As a general statement you don't care if an object is no longer needed. But this means that you need to be careful. Unlike C++ you don't have an explicit destructor. Therefore you need to make sure you clean up after anything like database connections before the object goes out of scope.

I guess I'm not a fan of System.gc() - before the JVM throws an OutOfMemoryException it will do everything it can to clean up memory. If you're calling System.gc() it may help a little bit but I guess I question that it is going to do much for you. A decent Java program doesn't need to do it - know where memory is allocated and make sure you don't have references to it when youd don't want them.

santo wrote:how does it know that the object is no longer needed by the prgm.

Overly simple explanation: the JVM will know to collect an object when it is no longer accessible by the code. Example: