public class Complex {
   Complex () { a = b = 0.0F; }
   Complex (float c, float d) { a = c; b = d; }
   Complex negate() { return new Complex(-a, -b); }
// or void negate() { a = -a; b = -b; }
   static Complex add(Complex x, Complex y) { 
      return new Complex(x.a + y.a, x.b + y.b); 
   }
   static Complex subtract(Complex x, Complex y) { 
      return add(x, y.negate()); 
   }
   static Complex multiply(Complex x, Complex y) { 
      return new Complex(x.a * y.a - x.b * y.b, x.a * y.b - x.b * y.a); 
   }
   public String toString() { 
      return "(" + a + ", " + b + ")"; 
   }
   private float a, b;
}