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

        al.add(10);
        al.add(20);
        al.add(30);
        al.add(1);
        al.add(2);
// This makes a call to remove(index) and 
// removes element 20.
        al.remove(1);        
// Now element 30 is moved one position back
// So element 30 is removed this time
        al.remove(1);