Simple Java HashMap example

       public class JavaHashMapExample
   {
     public static void main(String[] args)
     {
       //create object of HashMap
       HashMap hMap = new HashMap();
      
       /*
       Add key value pair to HashMap using
       Object put(Object key, Object value) method of Java HashMap class,
       where key and value both are objects
       put method returns Object which is either the value previously tied
       to the key or null if no value mapped to the key.
       */
      
       hMap.put("One", new Integer(1));
       hMap.put("Two", new Integer(2));
      
       /*
       Please note that put method accepts Objects. Java Primitive values CAN NOT
       be added directly to HashMap. It must be converted to corrosponding
       wrapper class first.
       */
      
       //retrieve value using Object get(Object key) method of Java HashMap class
       Object obj = hMap.get("One");
       System.out.println(obj);
      
       /*
       Please note that the return type of get method is an Object. The value must
       be casted to the original class.
       */
      
     }
   }