code: public static BufferedWriter getWriter(String path, String charsetName, boolean isAppend) throws IORuntimeException {
  		return getWriter(touch(path), Charset.forName(charsetName), isAppend);
  	}
docs: 获得一个带缓存的写入对象
  
  @param path 输出路径，绝对路径
  @param charsetName 字符集
  @param isAppend 是否追加
  @return BufferedReader对象
  @throws IORuntimeException IO异常