code: protected File getMinifiedFile(File input) {
          File output = getOutputFile(input);
          String ext = FilenameUtils.getExtension(output.getName());
          return new File(output.getParentFile().getAbsoluteFile(),
                  output.getName().replace("." + ext, cssMinifierSuffix + ".css"));
      }
docs: Creates out minified output file replacing the current extension with the minified one.
  
  @param input the file to minify.
  @return the output file where the minified code will go.