code: public static void closeWriter(String filePath) {
          Writer writer = writerCache.get(filePath);
          if (writer != null) {
              try {
                  writer.close();
              } catch (IOException e) {
                  e.printStackTrace();
              }
          }
          writerCache.remove(writer);
      }
docs: 关闭相应 file 的 writer
  @param filePath