code: public void setShowOutput(String mode) {
      try {
        this.outputMode = OutputMode.valueOf(mode.toUpperCase(Locale.ROOT));
      } catch (IllegalArgumentException e) {
        throw new IllegalArgumentException("showOutput accepts any of: "
            + Arrays.toString(OutputMode.values()) + ", value is not valid: " + mode);
      }
    }
docs: Display mode for output streams.