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

You might want to take a look at a BitSet The one used in Lucene is even faster as the standard Java implementation since it neglects some standard boundary checks.