Check if an ArrayList contains every element from another ArrayList (or Collection)

Question

There is probably a simple one-liner that I am just not finding here, but this is my question:

How do I check if an ArrayList contains all of the objects in another

Answer 1

You can use containsAll method of the list to do the check. However, this is a linear operation. If the list is large, you should convert it to HashSet first, and then perform containsAll:

HashSet tmp = new HashSet(one);
if (tmp.containsAll(two)) {
    ...
}

If the length of one is N and the length of two is M, this solution has time complexity of O(M+N); the "plain" containsAll has the complexity of O(M*N), which may be significantly worse.