Common elements in two lists

Question

I have two ArrayList objects with three integers each. I want to find a way to return the common elements of the two lists. Has anybody an idea how I can achiev

Answer 1

You can use set intersection operations with your ArrayList objects.

Something like this:

List l1 = new ArrayList();

l1.add(1);
l1.add(2);
l1.add(3);

List l2= new ArrayList();
l2.add(4);
l2.add(2);
l2.add(3);

System.out.println("l1 == "+l1);
System.out.println("l2 == "+l2);

List l3 = new ArrayList(l2);
l3.retainAll(l1);

    System.out.println("l3 == "+l3);

Now, l3 should have only common elements between l1 and l2.

CONSOLE OUTPUT
l1 == [1, 2, 3]
l2 == [4, 2, 3]
l3 == [2, 3]