TreeMap Class in Java

Example: Program to implement methods available in TreeMap class

import java.util.*;
public class TreeMapDemo
{
      public static void main(String args[])
      {
            TreeMap<Integer, String> tm = new TreeMap<Integer, String>();
            System.out.println("Initial size of TreeMap: "+tm.size());
            tm.put(2, "Green");
            tm.put(5, "Red");
            tm.put(3, "Black");
            tm.put(1, "White");
            tm.put(new Integer(7), "Orange");

            // tm.put(08,null); NullPointerException
            Set set = tm.entrySet();
            Iterator i = set.iterator();

            //Retriving the elemnt
            while(i.hasNext())
            {
                   Map.Entry me = (Map.Entry)i.next();
                   System.out.print(me.getKey() + ": ");
                   System.out.println(me.getValue());
            }
            System.out.println ("Size after addtion: "+tm.size());
            tm.remove(3);
            System.out.println ("Size after deletion: "+tm.size());
      }
}