How to check for night mode without using AppCompat.DayNight theme

MainActivity.java

package ca.llamabagel.daynight;

import android.content.res.Configuration;
import android.os.Bundle;
import android.os.PersistableBundle;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState, @Nullable PersistableBundle persistentState) {
        super.onCreate(savedInstanceState, persistentState);

        int nightFlag = getResources().getConfiguration().uiMode & Configuration.UI_MODE_NIGHT_MASK;

        TextView textView = findViewById(R.id.textView);

        switch (nightFlag) {
            case Configuration.UI_MODE_NIGHT_NO:
                textView.setText("Not Night Mode");
                break;
            case Configuration.UI_MODE_NIGHT_YES:
                textView.setText("Yes Night Mode");
                break;
            default:
                textView.setText("Probably not Night Mode");
                break;
        }
    }
}

MainActivity.kt

package ca.llamabagel.daynight

import android.content.res.Configuration
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import kotlinx.android.synthetic.main.activity_main.*

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val nightFlag = resources.configuration.uiMode and Configuration.UI_MODE_NIGHT_MASK

        textView.text = when (nightFlag) {
            Configuration.UI_MODE_NIGHT_NO -> "Not Night Mode"
            Configuration.UI_MODE_NIGHT_YES -> "Yes Night Mode"
            else -> "Probably not Night Mode"
        }
    }
}