针对java.io.FileNotFoundException open failed: EACCES (Permission denied)出现的问题，是由于当前使用的安卓版本过高导致的，出现了文件访问失败。

1\解决方法是在AndroidMainfest中添加android:requestLegacyExternalStorage="true"

2\AndroidMainfest中添加

<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

public void at_file()throws IOException {String sdcard=Environment.getDataDirectory().getPath().replace("data","sdcard");String test_p1=sdcard+test_p;//File file = new File(Environment.getExternalStorageDirectory(), "a.txt");File file=new File(sdcard,"a.txt");InputStream inputStream = new FileInputStream(file);BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));StringBuilder stringBuilder = new StringBuilder();String line;while ((line = reader.readLine()) != null) {stringBuilder.append(line);}String fileContent = stringBuilder.toString();System.out.println(fileContent);
}