code: public static void cMul(double a, double b, double c, double d, double[] results)
      {
          results[0] = a*c-b*d;
          results[1] = b*c+a*d;
      }
docs: Performs a complex multiplication
  
  @param a the real part of the first number
  @param b the imaginary part of the first number
  @param c the real part of the second number
  @param d the imaginary part of the second number
  @param results an array to store the real and imaginary results in. First index is the real, 2nd is the imaginary.