I have two ArrayList as follows:
ArrayList
original: 12, 16, 17, 19, 101
12, 16, 17, 19, 101
selected: 16, 19, 107, 108, 109
16, 19, 107, 108, 109
As an alternative, you could use CollectionUtils from Apache commons library. It has static intersection, union and subtract methods suitable for your case.