public double norm1(){
  double s=0;
  for (int i=0; i < size(); i++) {
    s+=Math.abs(V[i]);
  }
  return s;
}

public double norm1 ( ) { double s = 0 ; for ( int i = 0 ; i < size ( ) ; i ++ ) { s += Math . abs ( V [ i ] ) ; } return s ; }
returns the l1 - norm of the vector
