In Java 8, I use simple helper methods like this:
public static <T> Collection<T> getIntersection(Collection<T> coll1, Collection<T> coll2){
return Stream.concat(coll1.stream(), coll2.stream())
.filter(coll1::contains)
.filter(coll2::contains)
.collect(Collectors.toSet());
}
public static <T> Collection<T> getMinus(Collection<T> coll1, Collection<T> coll2){
return coll1.stream().filter(not(coll2::contains)).collect(Collectors.toSet());
}
public static <T> Predicate<T> not(Predicate<T> t) {
return t.negate();
}