java - find out the elements of an arraylist which is not present in another arraylist

Question

I have to find a best way to find out that elements which is not presented in the second arraylist. suppose

Arraylist a,b, 

Arraylist a={1,2,3,4,5};
Arraylist b={2,3,4};

So basically what I want is to find out that elements of a which is not present in arraylist b.

So what is the best solutions to do that?

Answer 1

List<Integer> c = new ArrayList<>(a);
c.removeAll(b);

Also consider to use Sets instead of Lists.