• State the behaviour that is guaranteed by the garbage collection system.
• Write code that explicitly makes objects eligible for garbage collection.
• Recognise the point in a piece of source code at which an object becomes eligible for garbage collection.

Garbage Collection

Memory Allocation

• at run-time
• method/local variables and method arguments(including references to objects) are allocated space on the stack
      - discarded when method returns
• objects (when created with new)
  • go on the heap
  • have a longer lifetime - only collected when nothing is referencing it anymore
  • eventually cleaned up by the garbage collector, which is a low-priority thread, straight after the JVM calls the object's finalize() method

System.gc() and Runtime.gc()

• suggests to the JVM to run the garbage collector
• garbage collection algorithm is platform dependant

Setting References to null

• when no longer using a reference, else can cause a memory leak - gc can't removed an object even though nothing is using it anymore
• eg. popping an object off a stack (implemented as an array) - don't just want to decrement the index to the array, but also set myStack[oldIndex] = null;