code: static int requireValidExponent(final int exponent) {
          if (exponent < MIN_EXPONENT) {
              throw new IllegalArgumentException("exponent(" + exponent + ") < " + MIN_EXPONENT);
          }
          if (exponent > MAX_EXPONENT) {
              throw new IllegalArgumentException("exponent(" + exponent + ") > " + MAX_EXPONENT);
          }
          return exponent;
      }
docs: Validates given exponent.
  
  @param exponent the exponent to validate.
  @return given exponent.