code: public static double max(double a, double b, double c, double d) {
      return a >= b ? //
          a >= c ? (a >= d ? a : d) : (c >= d ? c : d) : //
          b >= c ? (b >= d ? b : d) : (c >= d ? c : d);
    }
docs: Quadrary max, <i>without</i> handling of special values.
  
  Because of the lack of special case handling, this is faster than
  {@link Math#max}. But usually, it should be written inline.
  
  @param a First value
  @param b Second value
  @param c Third value
  @param d Fourth value
  @return Maximum