code: public static Path appendAndClose(String filePath, Charset charset,
              String writingString) {
          return new JMFileAppender(filePath, charset).append(writingString)
                  .closeAndGetFilePath();
      }
docs: Append and close path.
  
  @param filePath      the file path
  @param charset       the charset
  @param writingString the writing string
  @return the path