This generator uses multiple methods to highlight pros/cons of different approaches.

• Direct - uses brute force method of checking if number is a prime, by going through all of its possible divisors. It's optimised to go through minimal set of iterations and thus is very efficient.
• Set Sieve - sieve which uses bitset. It's fast, but limited to available memory
• Dictionary - version using dictionary for caching. It uses efficient primitive AVLTreeMap from FastUtil library. This library adds 17mb to the project, and is not justified here. It's purely to demonstrate an alternative approach.
• Direct Cached - uses optimised version with small cache of first 200 prime numbers.