code: public static int min(int a, int b, int c, int 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 min, <i>without</i> handling of special values.
  <p>
  Because of the lack of special case handling, this is faster than
  {@link Math#min}. But usually, it should be written inline.
  
  @param a First value
  @param b Second value
  @param c Third value
  @param d Fourth value
  @return minimum