Two small Java classes to encode and decode files using arithmetic coding. This implementation is designed to encode files using the optimal number of bytes and works for any alphabet size. Compared to other arithmetic coders, this implementation is probably slower but is guaranteed to have either an equivalent or better compression ratio.

Note: in the current version there is a non-zero probability that the decoder will incorrectly decode files. Verify the decoding process whenever a file is encoded to make sure that it works correctly.