List difference in java

Question

I have two ArrayList as follows:

original: 12, 16, 17, 19, 101

selected: 16, 19, 107, 108, 109

Answer 1

Here is a function to find intersection of various collections (more than 2) -

public static > C findIntersection(C newCollection,
                                                            Collection... collections) {
  boolean first = true;
  for (Collection collection : collections) {
      if (first) {
          newCollection.addAll(collection);
          first = false;
      } else {
          newCollection.retainAll(collection);
      }
  }
  return newCollection;
}

Usage -

public static void main(String[] args) {
  List l1 = List.of(1, 3, 5, 7, 9, 11, 13);
  List l2 = List.of(1, 2, 3, 5, 8, 13);
  List l3 = List.of(2, 3, 5, 7, 11, 13);
  Set intersection = findIntersection(new HashSet<>(), l1, l2, l3);
  System.out.println(intersection);
 }