Assume two lists:

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

Elements in list1 but not in list2

List<Integer> difference = list1.stream()
    .filter(e -> !list2.contains(e))
    .collect(Collectors.toList());

System.out.println(difference);

Output:

[1, 2]

Summary:

• .filter(e -> !list2.contains(e)) keeps elements only in the first list.
• .collect(Collectors.toList()) returns the result as a new list.
• For large lists, converting list2 to a Set improves performance.