java.lang.RuntimeException: 
  at android.app.ActivityThread.performLaunchActivity (ActivityThread.java:2751)
  at android.app.ActivityThread.handleLaunchActivity (ActivityThread.java:2812)
  at android.app.ActivityThread.-wrap12 (ActivityThread.java)
  at android.app.ActivityThread$H.handleMessage (ActivityThread.java:1528)
  at android.os.Handler.dispatchMessage (Handler.java:102)
  at android.os.Looper.loop (Looper.java:154)
  at android.app.ActivityThread.main (ActivityThread.java:6314)
  at java.lang.reflect.Method.invoke (Native Method)
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run (ZygoteInit.java:872)
  at com.android.internal.os.ZygoteInit.main (ZygoteInit.java:762)
Caused by: java.lang.IllegalStateException: 
  at io.realm.Realm.getDefaultInstance (Realm.java:327)
  at com.meisolsson.spotifyalarm.ui.base.BaseActivity.getRealm (BaseActivity.java:151)
  at com.meisolsson.spotifyalarm.ui.MainActivity.populateAdapter (MainActivity.java:119)
  at com.meisolsson.spotifyalarm.ui.MainActivity.setupRecyclerView (MainActivity.java:115)
  at com.meisolsson.spotifyalarm.ui.MainActivity.onCreate (MainActivity.java:56)
  at android.app.Activity.performCreate (Activity.java:6757)
  at android.app.Instrumentation.callActivityOnCreate (Instrumentation.java:1119)
  at android.app.ActivityThread.performLaunchActivity (ActivityThread.java:2704)

public class Application extends android.app.Application {

    @Override
    public void onCreate() {
        ...
        Realm.init(this);
        RealmConfiguration configuration = new RealmConfiguration.Builder()
                .schemaVersion(2)
                .migration(new AlarmifyMigration())
                .build();

        Realm.setDefaultConfiguration(configuration);
        realm = Realm.getDefaultInstance();
        ....
        super.onCreate();
    }
}

public abstract class BaseActivity extends AppCompatActivity {
    private Realm realm;
    ...
    /**
     * @return Instance of {@link Realm}.
     */
    public Realm getRealm() {
        if (realm == null || realm.isClosed()) {
            realm = Realm.getDefaultInstance();
        }

        return realm;
    }
}