Set cause for custom exception

Question

I'd been trying to set ArrayIndexOutOfBoundsException as cause of NoSuchUserException(for MyUser.class),but it doesn't work. The Throwable parameter represents the cause of the exception. Can someone tell me what am I missing?

   public class NoSuchUserException extends Exception {
        private int id = 0;
        private Throwable cause;
          public NoSuchUserException(int id, Throwable x) {
            super("User " + id + " does not exist");
            this.cause = x;
        }
    }

    import java.util.Arrays;
    public class MyUser {
        private String[] users;

        public MyUser(String[] users) {
            this.users = Arrays.copyOf(users, users.length);
        }

        public String getUser(int id) throws NoSuchUserException {
            try {
                someMethodThatThrows();
            } catch (ArrayIndexOutOfBoundsException e) {

                throw new NoSuchUserException(id, e);
            }

            return users[id];
        }

        private void someMethodThatThrows() {
            throw new ArrayIndexOutOfBoundsException("");
        }
    }

Answer 1

You can simply pass the cause to the parent constructor:

public class NoSuchUserException extends Exception {
    public int id = 0;
    public NoSuchUserException(int id, Throwable x) {
        super("User " + id + " does not exist", x);
        this.id = id;
    }
}

See the documentation.