Intersection and union of ArrayLists in Java

Question

Are there any methods to do so? I was looking but couldn\'t find any.

Another question: I need these methods so I can filter files. Some are AND filter

Answer 1

In Java 8, I use simple helper methods like this:

public static  Collection getIntersection(Collection coll1, Collection coll2){
    return Stream.concat(coll1.stream(), coll2.stream())
            .filter(coll1::contains)
            .filter(coll2::contains)
            .collect(Collectors.toSet());
}

public static  Collection getMinus(Collection coll1, Collection coll2){
    return coll1.stream().filter(not(coll2::contains)).collect(Collectors.toSet());
}

public static  Predicate not(Predicate t) {
    return t.negate();
}