Вы можете использовать метод removeall
Коллекция listOne = new ArrayList (Arrays.asList ("x", "y", "z", "a", "b", "c", "d"«));Коллекция listTwo = new ArrayList (Arrays.asList ("a", "b", "d", "e", "f", "x", "y"));
List<String> sourceList = new ArrayList<String>(listOne);
List<String> destinationList = new ArrayList<String>(listTwo);
sourceList.removeAll( listTwo );
destinationList.removeAll( listOne );