Android : How to kill process after my android app exit?

After I pressed back key to exit my android app, the process of this app still exists:

$ adb shell ps |grep -is accelerometerplay
u0_a122   2679  139   504048 23968 ffffffff 400d13c4 S com.example.android.accelerometerplay

I add some code in onDestroy():

@Override
public void onDestroy() {
    super.onDestroy();

    android.os.Process.killProcess(android.os.Process.myPid());
}

Is this enough? Or I have to do some extra things?