Java HashMap sort on key value vis TreeMap

import java.util.HashMap;
import java.util.Map;
import java.util.TreeMap;

public class Main {

  public static void main(String[] args) {
    HashMap<String, String> hm = new HashMap<String, String>();
    hm.put("4", "four");
    hm.put("3", "Java");
    hm.put("1", "CSS");

    hm.put("5", "CSS");
    hm.put("6", "HTML");

    hm.put("0", "CSS");
    hm.put("2", "HTML");

    System.out.println(hm);/*  w w  w  .ja v a 2 s .c om*/
    
    Map<String, String> treeMap = new TreeMap<String, String>(hm);
    System.out.println(treeMap);
    
  }
}