Heap management and garbage collection

• An object is created by invoking a constructor by means of the new operator. The moment an object is created, the memory locations for the object are allocated on the heap.
• When an object is not used anymore by the program, the memory locations allocated on the heap for the object can be freed and made available for other objects. In Java, differently from other languages, the programmer cannot choose to do such an operation explicitly. It is done automatically by the garbage collector when the object is not accessible anymore.

The garbage collector is a component of the JVM that is able to detect when an object has no more references that can be used to access the object, and hence is not usable anymore and can be deallocated. Typically, the garbage collector is invoked automatically by the JVM, without any control by the programmer, when it is necessary to make memory available. However, the programmer can also choose to invoke the garbage collector explicitly, by calling the static method gc() of the class System.