HashMap Example

 /*  
 Hash Map allows null for both key and values.   
 we will see that in this program.   
 Author; itsafiz@gmail.com  
 */  
 import java.util.*;   
 import java.util.Iterator;   
 class HashMapTest  
 {  
      public static void main(String[]args)  
      {  
      HashMap<String, Integer> name = new HashMap<String,Integer>();   
      name.put("one",1);  
      name.put("two",2);  
      name.put("three",3);  
      name.put("four",null);  
      // printing all the keys ....   
      Set<String> keys = name.keySet(); // returns entire key set in the Map  
      Iterator item = keys.iterator();   
      while(item.hasNext())  
           {  
                String s = item.next().toString();   
                System.out.println(s+" = "+name.get(s));// get() method returns value   
           }  
      }  
 }