You do not need to explicitly allocate or deallocate memory in
Java. Memory is allocated as needed, both on the stack and the
heap, and reclaimed by the garbage collector when it is
no longer needed. There's no malloc(), free(), or destructor methods.
There are constructors and these do allocate memory on the heap, but this is transparent to the programmer.
The exact algorithm used for garbage collection varies from one virtual machine to the next. The most common approach in modern VMs is generational garbage collection for short-lived objects, followed by mark and sweep for longer lived objects. I have never encountered a Java VM that used reference counting.