Notifications in Android Studio

XML

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".NotificationActivity">

</androidx.constraintlayout.widget.ConstraintLayout>

JAVA

package com.nilscreation.mytestapp;

import androidx.appcompat.app.AppCompatActivity;
import androidx.core.content.res.ResourcesCompat;

import android.app.Notification;
import android.app.NotificationChannel;
import android.app.NotificationManager;
import android.graphics.Bitmap;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.os.Bundle;

public class NotificationActivity extends AppCompatActivity {

    private static final String CHANNEL_ID = "My Channel";
    private static final int NOTIFICATION_ID = 100;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_notification);

        Drawable drawable = ResourcesCompat.getDrawable(getResources(), R.drawable.emoji, null);
        BitmapDrawable bitmapDrawable = (BitmapDrawable) drawable;
        Bitmap largeIcon = bitmapDrawable.getBitmap();

        NotificationManager nm = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
        Notification notification;

        if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
            notification = new Notification.Builder(this)
                    .setLargeIcon(largeIcon)
                    .setSmallIcon(R.drawable.emoji)
                    .setContentTitle("Title Text Here")
                    .setContentText("Text Here")
                    .setSubText("Sub Text Here")
                    .setChannelId(CHANNEL_ID)
                    .build();

            nm.createNotificationChannel(new NotificationChannel(CHANNEL_ID, "new channel", NotificationManager.IMPORTANCE_HIGH));

        } else {
            notification = new Notification.Builder(this)
                    .setLargeIcon(largeIcon)
                    .setSmallIcon(R.drawable.emoji)
                    .setContentTitle("Title Text Here")
                    .setContentText("Text Here")
                    .setSubText("Sub Text Here")
                    .build();
        }

        nm.notify(NOTIFICATION_ID, notification);
    }
}

OUTPUT