General classes/source code for solving Java algorithmic problems? [closed]

Question

I need to build a small repository of algorithms with implementation and description. I found recently, for example, an efficient permutations generator for permutations of arbitrary length. Where can I find full source code implementations with short descriptions of other such algorithms?

Anything covered in the Java API is not needed, so I don't need Euclid's algorithm for GCD, as that's implemented in BigInteger.

Solutions for max-flow/prims/etc. are all welcome, as well as any useful algorithm-solving/creating Java tools.

Answer 1

1. Apache commons-math
2. COLT from CERN
3. Apache Mahout