code: protected String evaluateOutputDirectory(final String outputDir, final String inputDir) {
      return outputDir != null && !outputDir.trim().isEmpty() ? outputDir : inputDir.trim();
    }
docs: Evaluates and returns the output directory.
  
  <p>
  If the passed {@code outputDir} is {@code null} or empty, the passed {@code inputDir} otherwise
  the {@code outputDir} will returned.
  
  @param outputDir could be {@code null} or empty
  @param inputDir must not be {@code null}
  
  @return never {@code null}
  
  @throws NullPointerException if passed {@code inputDir} is {@code null}
  
  @since 1.2.0