sub list without modifying original list in java

Question

Below code actually modifies original list x. Is there anyway to sub list the main list considering that modification to sub list should not modify the original list?

List<Integer> x = new ArrayList<Integer>();

x.add(1);
x.add(2);
x.add(3);
x.add(4);
x.add(5);

List<Integer> y = new ArrayList<Integer>();

y.add(1);
y.add(2);
y.add(3);

final List<Integer> z = x.subList(0, 4);

System.out.println("sublist " + z.toString());

z.removeAll(y);

System.out.println("Main list after removing sublist " + x.toString());

Result:

sublist [1, 2, 3, 4]
Main list after removing sublist [4, 5]

Answer 1

Try to use List<Integer> z = new ArrayList<>(x.subList(0, 4))

   List<Integer> x = new ArrayList<Integer>();
    x.add(1);
    x.add(2);
    x.add(3);
    x.add(4);
    x.add(5);

    List<Integer> y = new ArrayList<Integer>();
    y.add(1);
    y.add(2);
    y.add(3);

    final List<Integer> z = new ArrayList<>(x.subList(0, 4));

    System.out.println("sublist " + z.toString());

    z.removeAll(y);

    System.out.println("Main list after removing sublist " + x.toString());

Output:

sublist [1, 2, 3, 4]
Main list after removing sublist [1, 2, 3, 4, 5]

Answer 2

If you do not want the sublist to be a "window" into the original, you need to make a copy, like this:

final List<Integer> z = new ArrayList<Integer>(x.subList(0, 4));

If you would rather have an unmodifiable list without making a copy, you could use Collections.unmodifiableList:

final List<Integer> z = Collections.unmodifiableList(x.subList(0, 4));
z.removeAll(y); // <<== This will now fail.