Immutable.java

void immutable() {
    List<Integer> ints = List.of(1, 2, 3, 4, 5, 6);
    List<Integer> evenInts = extractEvenInts(ints);
    System.out.println(evenInts); // prints -> [2, 4, 6]
    System.out.println(ints); // prints -> [1, 2, 3, 4, 5, 6]
}