A space efficient data structure to store and look-up through a large set of (uniformly distributed) Integers

Question

I\'m required to hold, in memory, and look-up through one million uniformly distributed integers. My workload is extremely look-up intensive.
My current implementation u

Answer 1

There are some IntHashSet implementations for primitives available.

Quick googling got me this one. There is also an apache [open source] implementation of IntHashSet. I'd prefer the apache implementation, though it has some overhead [it is implemented as a IntToIntMap]