Java Performance - ArrayLists versus Arrays for lots of fast reads

Question

I have a program where I need to make 100,000 to 1,000,000 random-access reads to a List-like object in as little time as possible (as in milliseconds) for a cellular automa

Answer 1

If you're creating the list once, and doing thousands of reads from it, the overhead from ArrayList may well be slight enough to ignore. If you're creating thousands of lists, go with the standard array. Object creation in a loop quickly goes quadratic, simply because of all the overhead of instantiating the member variables, calling the constructors up the inheritance chain, etc.

Because of this -- and to answer your second question -- stick with standard ints rather than the Integer class. Profile both and you'll quickly (or, rather, slowly) see why.