List throws ConcurrentModificationException but set does not throws ConcurrentModificationException? [duplicate]

Answer 1

 public static void main(String[] ar) {
            List list = new ArrayList();
            list.add("core java");
            list.add("php");
            list.add("j2ee");
            list.add("struts");
            list.add("hibernate");

            Iterator itr = list.iterator();

            while (itr.hasNext()) {
                System.out.println(itr.next());
            }
            list.remove("php");

          /*  while (itr.hasNext()) {
                System.out.println(itr.next());
            }*/

        }

problem in itr object.it holds the list object reference