string reverse word by word

import java.util.*;
class rev_WbW {
String st="";
void input()
{
        Scanner in=new Scanner(System.in);
        System.out.println("enter a sentence :");
        st=in.nextLine();
}
void rev()
{
   String s2="";
   StringTokenizer s1 = new StringTokenizer(st," ");
    while (s1.hasMoreTokens())
     {
         /* Prints the elements from the String */
        s2=s1.nextElement()+" "+s2;
     }
        System.out.println(s2);

}
        public static void main(String[] args) {
        rev_WbW ob=new rev_WbW();
        ob.input();
        ob.rev();
    }
}