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

Intersection of two list of different object based on common key - Java 8

 private List intersection(List users, List list) {

        return list.stream()
                .flatMap(OtherUser -> users.stream()
                        .filter(user -> user.getId()
                                .equalsIgnoreCase(OtherUser.getId())))
                .collect(Collectors.toList());
    }