code: public static String read(FileChannel fileChannel, String charsetName) throws IORuntimeException {
  		return read(fileChannel, CharsetUtil.charset(charsetName));
  	}
docs: 从FileChannel中读取内容，读取完毕后并不关闭Channel
  
  @param fileChannel 文件管道
  @param charsetName 字符集
  @return 内容
  @throws IORuntimeException IO异常