how calculate java array memory usage

Question

If I have:

int c[] = new int[10];

and

int a[][] = new int[2][3];

and in generally

an n*m*..

Answer 1

If you want an accurate answer, you can't. At least not in any easy way. This thread explains more.

The trouble with Bragaadeesh's and Bakkal's answers are that they ignore overhead. Each array also stores things like the number of dimensions it has, how long it is and some stuff the garbage collector uses.

For a simple estimate, you should be fine by using the calculations from the other answers and adding 100-200 bytes.