java读取文件内容为string字符串的方法

/** * 读出城市列表文件 */ private String readCityFile() {  File file02 = new File(path_xinfu, "/cityList.json");  FileInputStream is = null;  StringBuilder stringBuilder = null;  try {   if (file02.length() != 0) {    /**     * 文件有内容才去读文件     */    is = new FileInputStream(file02);    InputStreamReader streamReader = new InputStreamReader(is);    BufferedReader reader = new BufferedReader(streamReader);    String line;    stringBuilder = new StringBuilder();    while ((line = reader.readLine()) != null) {     // stringBuilder.append(line);     stringBuilder.append(line);    }    reader.close();    is.close();   } else {    mLoadingLayout.setStatus(LoadingLayout.Empty);   }  } catch (Exception e) {   e.printStackTrace();  }  return String.valueOf(stringBuilder); }