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Java Iterator Example

Submitted by Andr on Tue, 10/26/2010 - 19:57

Java Examples

/*
Java Iterator example.
This Java Iterator example describes how Iterators are used with Collections.
*/
 
import java.util.Iterator;
import java.util.HashMap;
 
public class IteratorExample{
    
    public static void main(String args[]){
    
        HashMap hashMap = new HashMap(); // Constructs a new empty HashMap
       
        hashMap.put("One", new Integer(1)); //adding value to HashMap        
        hashMap.put("Two", new Integer(2));        
        hashMap.put("Three", new Integer(3));
       
        System.out.println("Retrieving all keys from the HashMap");
       
        //retrieve iterator from keySet of the HashMap        
        Iterator iterator = hashMap.keySet().iterator();
       
        /*
       
        Iterators hasNext() method returns true if it has more element,        
        otherwise it returns false.
       
        Iterator's next() method returns the current element of underlying collection.
       
        IMPORTANT : It returns an Object, so we need to downcast it.
       
        */
       
        while(iterator. hasNext()){        
            System.out.println(iterator.next());    
        }
    
    }
 
}
 
/*
OUTPUT of the above given Java Iterator Example would be:
Retrieving all keys from the HashMap
Three
Two
One
*/

Andr's blog

I was hoping to see an

Submitted by Anonymous on Fri, 01/14/2011 - 17:29.

I was hoping to see an example of the needed downcast

Nice article , just to add

Submitted by javabuddy on Sun, 03/06/2011 - 10:56.

Nice article , just to add the functionality of Enumeration interface is duplicated by the Iterator interface. Iterator has a remove() method while Enumeration doesn't. Enumeration acts as Read-only interface, because it has the methods only to traverse and fetch the objects, where as using Iterator we can manipulate the objects also like adding and removing the objects. to read more see here difference between iterator and enumeration

nice example.

Submitted by Anonymous on Thu, 09/15/2011 - 11:27.

nice example.

I see Iterator similar to

Submitted by Anonymous on Tue, 10/04/2011 - 09:50.

I see Iterator similar to ArrayList.Who can explain difference between Iterator and ArrayList for me?Thanks a lot

Collection and Iterator is

Submitted by Anonymous on Mon, 11/07/2011 - 20:43.

Collection and Iterator is two different thing, Iterator is used to navigate objects from collection e.g. ArrayList, HashSet etc. for more information check What is Iterator in Java