import java.util.Hashtable;

 public class HashTable {

 public static void main (String[] args)

 {

     Hashtable<String,Object> ht=new Hashtable<String,Object>();

     ht.put("xiao wang", 30);

     ht.put("zhang san", "aaa");

     ht.put("he hai", true);

     System.out.println(ht.size());

     ht.remove("zhang san");

     System.out.println(ht.size());

     System.out.println(ht.get("he hai"));

      ht.put("he hai", "hello");

      System.out.println(ht.get("he hai"));

 }

 }