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

This post is fairly old, but nevertheless it was the first one popping up on google when looking for that topic.

I want to give an update using Java 8 streams doing (basically) the same thing in a single line:

List intersect = list1.stream()
    .filter(list2::contains)
    .collect(Collectors.toList());

List union = Stream.concat(list1.stream(), list2.stream())
    .distinct()
    .collect(Collectors.toList());

If anyone has a better/faster solution let me know, but this solution is a nice one liner that can be easily included in a method without adding a unnecessary helper class/method and still keep the readability.