/*
    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
    */