/*

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 into HashMap

hashMap.put( "Two", new Integer(2) );

hashMap.put( "Three", new Integer(3) );

System.out.println("Retriving all keys from the HashMap");

//retrive 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 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 :

Retriving all keys from the HashMap

Three

Two

One

*/