Question

I have two arraylists, where each of which stores a set of elements. I would like to obtain and output the intersection of these two sets. Is there any efficient and elegant way of achieve this? How about union?

Answer 1

HashSet s0 = new HashSet(arraylist0);
s0.retainAll(arraylist1);
System.out.println("Intersection: " + s0);

s0 = new HashSet(arraylist0);
s0.addAll(arraylist1);
System.out.println("Union: " + s0);