Set - Collection has quadratic complexity

org.codehaus.groovy.runtime.DefaultGroovyMethods#minus(Set<T> self, Collection<?> removeMe)'s complexity is O(m*n). If you used something like THashSet (http://trove4j.sourceforge.net/javadocs/gnu/trove/set/hash/THashSet.html) you could make it O(m+n) by plugging in a smart hashing strategy. Perhaps you already have something similar in your codebase or dependencies?