List difference in java

Question

I have two ArrayList<Integer> as follows:

original: 12, 16, 17, 19, 101

selected: 16, 19, 107, 108, 109

I want to do difference on these lists such that in the end I have two lists:

Add: 108,109,107

remove: 12, 17, 101

Length of original and selected lists varies and one can be greater/smaller than the other

Answer 1

As an alternative, you could use CollectionUtils from Apache commons library. It has static intersection, union and subtract methods suitable for your case.

Answer 2

List<Integer> original = Arrays.asList(12,16,17,19,101); List<Integer> selected = Arrays.asList(16,19,107,108,109);  ArrayList<Integer> add = new ArrayList<Integer>(selected); add.removeAll(original); System.out.println("Add: " + add);  ArrayList<Integer> remove = new ArrayList<Integer>(original); remove.removeAll(selected); System.out.println("Remove: " + remove); 

Output:

Add: [107, 108, 109] Remove: [12, 17, 101] 

Uses Collection's removeAll method. See javadocs.