Source code TreeMap

package myutil;

import java.util.TreeMap;

public class TreeMapEx1 {
    public static void main(String[] args) 
    {
        TreeMap map=new TreeMap();
    map.put(new Integer(100),"orange");
    map.put(new Integer(200) ,"apple");
    map.put(new Integer(300),"grapes");

    //enter the existing key it overirde old data
    System.out.println(map.put(new Integer(300),"banana"));
    System.out.println("The TreeeMap Is "+map);

    //try to add hetrogineous(different) objects as value
    map.put(new Integer(400),new Integer(10));  // no error

     //    try to add hetrogineous(different) objects as key 
    //  map.put("fsdf",new Integer(10));  // exception

    System.out.println("The TreeeMap Is "+map);
//    Try to place the null you will get NullPointerException
    // map.put(null,"javasun");   //exception
      }
}

output:
grapes
The TreeeMap Is {100=orange, 200=apple, 300=banana}
The TreeeMap Is {100=orange, 200=apple, 300=banana, 400=10}