What is the difference between Enumeration and Iterator?

What is the difference between Enumeration and Iterator?

Enumeration

 Ø When the Enumeration interface is implemented by an object, that object can generate a sequence of elements.

 Ø This was introduced in JDK 1.0 .

 Ø The method hasMoreElements() will test if this enumeration contains more elements and the nextElement() returns the next element in the sequence (if there is at least one more to go).

Example:-

         Enumeration e = v1.elements();// v1 is an object of Vector

        while(e.hasMoreLements()){

        System.out.println(e.nextElement());

      }

Iterator

  Which allows iterating through elements of the collections objects that implement the Collections framework (such as ArrayList, LinkedList, etc.).

   Ø This was introduced in JDK 1.2 and replaced the Enumerator within the Java Collections Framework.

  Ø Unlike Enumeration, Iterator is fail-safe.This means that concurrent modifications (to the underlying collection) are not allowed when Iterator is used.

  Ø This is very useful in multi-threaded environments where there is always a risk of concurrent modifications.

  Ø In the event of a concurrent modification, the Iterator object will throw a ConcurrentModificationException.

  Ø Iterator has shorter method names compared to Enumerator.

  Ø Furthermore, iterator has the additional functionality of deleting elements during the iteration (which is not possible using Enumerator).

  Ø So, if there is a need to remove elements from the collection, Iterator is the only option that can be considered.

Example:-

      Iterator i = v1.elements();// v1 is an object of Vector

       while(i.hasNext()){

        System.out.println(e.next());

      }