Here is an example of HashMap.

import java.util.*;

public class HashMapExample{

  public static void main(String[] args){
    HashMap hm = new HashMap();
    hm.put(1,"A");
    hm.put(2,"B");
    hm.put(1,"C");
    hm.put(3,"D");
    hm.put(4,"E");

    Set set = hm.entrySet();

    Iterator i = set.iterator();

    while(i.hasNext()){
      Map.Entry me = (Map.Entry)i.next();
      System.out.println(me.getKey() + " : " + me.getValue() );
    }
  }
}