How does size( ) works in java's ArrayList class?

Question

So, in order to get the most efficient code, I really wanted to know how does the size() method in Java ArrayList work... Does it count every element, going through all the positions, like a simple list? or does it just gets the size by the last index registered?

Thanks in advance!

Answer 1

Never hurts to look in the source code:

public int size() {
    return size;
}

It returns an instance variable - pretty damn fast.