collections class binarysearch

package myutil;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class CollectionsSearch {
     public static void main(String [] args )  {
         List l=new ArrayList();
            l.add("Z");
            l.add("A");
            l.add("H");
            l.add("E");
            l.add("O");
            l.add("B");
            l.add("F");
            l.add("Y");
    Collections.sort(l);  //before binarysearch we have to sort
    System.out.println(Collections.binarySearch(l,"A"));  
    System.out.println(Collections.binarySearch(l,"F")); 
    System.out.println(Collections.binarySearch(l,"M")); 
    }
}

output:
0
3
-6