Multiset in Java

You only need one single file: https://github.com/claudemartin/multiset/blob/master/Multiset/src/ch/claude_martin/Multiset.java

There's spotbugs-annotations-3.1.0.jar because I'm using SpotBugs. But you could just as well delete these annotations.

My Blog: https://humanoidreadable.wordpress.com/2015/02/20/multiset-in-java/