code: public static File replaceExtension(File file, String newExtension) throws IllegalArgumentException
    {
      Params.notNull(file, "File");
      return new File(replaceExtension(file.getPath(), newExtension));
    }
docs: Replace extension on given file and return resulting file.
  
  @param file file to replace extension,
  @param newExtension newly extension.
  @return newly created file.
  @throws IllegalArgumentException if file parameter is null.