如何使用的一个例子的 openFileInput 的：

An example of how to use openFileInput:

    FileInputStream in = openFileInput("filename.txt");
    InputStreamReader inputStreamReader = new InputStreamReader(in);
    BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
    StringBuilder sb = new StringBuilder();
    String line;
    while ((line = bufferedReader.readLine()) != null) {
        sb.append(line);
    }