Javaでリストの差分を得る方法（A-B）

List<Integer> list1 = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5));
List<Integer> list2 = new ArrayList<>(Arrays.asList(2, 4));

list1.removeAll(list2);
System.out.println(list1); // [1, 3, 5]

List<Integer> list1 = Arrays.asList(1, 2, 3, 4, 5);
List<Integer> list2 = Arrays.asList(3, 4, 5, 6, 7);

Collection<Integer> diff = CollectionUtils.subtract(list1, list2);

System.out.println(diff);