private void dialogSettings() {
    final Dialog dialog = new Dialog(this, R.style.dialog_style);
    dialog.setContentView(R.layout.dialog_settings);
    final CheckBox sound = (CheckBox) dialog.findViewById(R.id.checkBoxSound);
    final CheckBox vibration = (CheckBox) dialog.findViewById(R.id.checkBoxVibration);
    final SharedPreferences pref = getSharedPreferences("SETTINGS", 0);
    sound.setChecked(pref.getBoolean("SOUND", true));
    vibration.setChecked(pref.getBoolean("VIBRATION", true));
    Button buttonSave = (Button) dialog.findViewById(R.id.buttonSave);
    buttonSave.setOnClickListener(new OnClickListener() {
        public void onClick(View v) {
            SharedPreferences.Editor editor = pref.edit();
            editor.putBoolean("SOUND", sound.isChecked());
            editor.putBoolean("VIBRATION", vibration.isChecked());
            editor.commit();
            dialog.dismiss();
        }
    });
    dialog.show();
}

private boolean SOUND;

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.game_normal_layout);
    SharedPreferences pref = getSharedPreferences("SETTINGS", 0);
    SOUND = pref.getBoolean("SOUND", true);
    ....
}

private void evaluateAnswer() {
    if(correct) {
        if(SOUND) {  // LINE 259
            ding.seekTo(0);
            ding.start();
        }
    ...
}

java.lang.NullPointerException
at mindmApp.quiz.GameNormalActivity.evaluateAnswer(GameNormalActivity.java:259)