get byte or memory size of array,list,collections in java

In java lot of time we will come across the scenerio where in which we need to find the how much memory used by given list.

The ArrayList holds a pointer to a single Object array, which grows as the number of elements exceed the size of the array. The ArrayList's underlying Object array grows by about 50% whenever we run out of space.

ArrayList also writes out the size of the underlying array, used to recreate an identical ArrayList to what was serialized.

sample code to get the memory size the collection in bytes