Java TreeMap.firstKey()

public K firstKey()

import java.util.TreeMap;
// w w w.  j  a v  a 2  s .c  om
public class Main {
   public static void main(String[] args) {
      
      TreeMap<Integer, String>  treemap = new TreeMap<Integer, String> ();
      
      // populating tree map
      treemap.put(2, "two");
      treemap.put(1, "one");
      treemap.put(3, "three");
      treemap.put(6, "six");
      treemap.put(5, "from java2s.com");
      
      System.out.println("Checking first key");
      System.out.println("First key is: "+ treemap.firstKey());
   }    
}