public static<T extends Comparable<T>> int Binary2Search (T key,List pl){
                  return search(key,pl,0,pl.listSize()-1);
    }

    public static<T extends Comparable<T>> int search (T key,List<T> pl,int bottom,int top ){
        int  middle ;
        if (top>=bottom){
            middle=  (top+bottom)/2;
            if (key==(pl.retreiveList(middle)))
                return middle;
            if (key.compareTo(pl.retreiveList(middle))<0){
                return  search(key,pl,bottom,middle-1);
            }
            else
                return search(key, pl, middle + 1, top) ;

        }
        return -1;
    }