File read error in new android OS 5.0.1

Question

I am working with file in android. I used below code and it worked well in Note 2 that used OS 4.4.2. However, It appeared the error as below report when I run in OS 5.0.1 (Galaxy S4). What is happen in my code? Could you suggest for me to solve it

private boolean checkAudioFile()
{
    ArrayList<String> datacheck=null;
    try{
    String filepath = Environment.getExternalStorageDirectory().getPath();
    String filename=filepath+"/" + FILE_FOLDER +  "/" + "file_list.txt" ;
    BufferedReader in = new BufferedReader(new FileReader(filename));
    String audio_name;
    datacheck = new ArrayList<String>();
    while ((audio_name = in.readLine()) != null) {                  
        datacheck.add(audio_name);
    }
    in.close();

    } catch (IOException e) {
        System.out.println("File Read Error");
    }
    if(datacheck.isEmpty())
        return true;
    else
        return false;
}

This is my error in OS 5.0.1

11-16 20:42:48.483: I/System.out(16967): File Read Error
11-16 20:42:48.483: D/AndroidRuntime(16967): Shutting down VM
11-16 20:42:48.483: E/AndroidRuntime(16967): FATAL EXCEPTION: main
11-16 20:42:48.483: E/AndroidRuntime(16967): Process: com.example.readfileapp, PID: 16967
11-16 20:42:48.483: E/AndroidRuntime(16967): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.readfileapp/com.example.readfileapp.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.util.ArrayList.isEmpty()' on a null object reference
11-16 20:42:48.483: E/AndroidRuntime(16967):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2693)
11-16 20:42:48.483: E/AndroidRuntime(16967):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2758)
11-16 20:42:48.483: E/AndroidRuntime(16967):    at android.app.ActivityThread.access$900(ActivityThread.java:177)
11-16 20:42:48.483: E/AndroidRuntime(16967):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1448)
11-16 20:42:48.483: E/AndroidRuntime(16967):    at android.os.Handler.dispatchMessage(Handler.java:102)
11-16 20:42:48.483: E/AndroidRuntime(16967):    at android.os.Looper.loop(Looper.java:145)
11-16 20:42:48.483: E/AndroidRuntime(16967):    at android.app.ActivityThread.main(ActivityThread.java:5942)
11-16 20:42:48.483: E/AndroidRuntime(16967):    at java.lang.reflect.Method.invoke(Native Method)
11-16 20:42:48.483: E/AndroidRuntime(16967):    at java.lang.reflect.Method.invoke(Method.java:372)
11-16 20:42:48.483: E/AndroidRuntime(16967):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
11-16 20:42:48.483: E/AndroidRuntime(16967):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
11-16 20:42:48.483: E/AndroidRuntime(16967): Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.util.ArrayList.isEmpty()' on a null object reference
11-16 20:42:48.483: E/AndroidRuntime(16967):    at com.example.readfileapp.MainActivity.checkAudioFile(MainActivity.java:622)
11-16 20:42:48.483: E/AndroidRuntime(16967):    at com.example.readfileapp.MainActivity.onCreate(MainActivity.java:172)
11-16 20:42:48.483: E/AndroidRuntime(16967):    at android.app.Activity.performCreate(Activity.java:6289)
11-16 20:42:48.483: E/AndroidRuntime(16967):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
11-16 20:42:48.483: E/AndroidRuntime(16967):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2646)
11-16 20:42:48.483: E/AndroidRuntime(16967):    ... 10 more

Answer 1

You need to perform a null check.

You ArrayList can be empty but also it can be null and then you cant call isEmpty()

Change it to this:

if(datacheck!=null && datacheck.isEmpty())

Hope this helps.