NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(this, CHANNEL_ID)
        .setSmallIcon(R.drawable.notification_icon)
        .setContentTitle(textTitle)
        .setContentText(textContent)
        .setPriority(NotificationCompat.PRIORITY_DEFAULT);

NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(this, CHANNEL_ID)
        .setSmallIcon(R.drawable.notification_icon)
        .setContentTitle("My notification")
        .setContentText("Much longer text that cannot fit one line...")
        .setStyle(new NotificationCompat.BigTextStyle()
                .bigText("Much longer text that cannot fit one line..."))
        .setPriority(NotificationCompat.PRIORITY_DEFAULT);

private void createNotificationChannel() {
    // Create the NotificationChannel, but only on API 26+ because
    // the NotificationChannel class is new and not in the support library
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        CharSequence name = getString(R.string.channel_name);
        String description = getString(R.string.channel_description);
        int importance = NotificationManager.IMPORTANCE_DEFAULT;
        NotificationChannel channel = new NotificationChannel(CHANNEL_ID, name, importance);
        channel.setDescription(description);
        // Register the channel with the system; you can't change the importance
        // or other notification behaviors after this
        NotificationManager notificationManager = getSystemService(NotificationManager.class);
        notificationManager.createNotificationChannel(channel);
    }
}

// Create an explicit intent for an Activity in your app
Intent intent = new Intent(this, AlertDetails.class);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, 0);

NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(this, CHANNEL_ID)
        .setSmallIcon(R.drawable.notification_icon)
        .setContentTitle("My notification")
        .setContentText("Hello World!")
        .setPriority(NotificationCompat.PRIORITY_DEFAULT)
        // Set the intent that will fire when the user taps the notification
        .setContentIntent(pendingIntent)
        .setAutoCancel(true);

NotificationManagerCompat notificationManager = NotificationManagerCompat.from(this);

// notificationId is a unique int for each notification that you must define
notificationManager.notify(notificationId, mBuilder.build());

Intent snoozeIntent = new Intent(this, MyBroadcastReceiver.class);
snoozeIntent.setAction(ACTION_SNOOZE);
snoozeIntent.putExtra(EXTRA_NOTIFICATION_ID, 0);
PendingIntent snoozePendingIntent =
        PendingIntent.getBroadcast(this, 0, snoozeIntent, 0);

NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(this, CHANNEL_ID)
        .setSmallIcon(R.drawable.notification_icon)
        .setContentTitle("My notification")
        .setContentText("Hello World!")
        .setPriority(NotificationCompat.PRIORITY_DEFAULT)
        .setContentIntent(pendingIntent)
        .addAction(R.drawable.ic_snooze, getString(R.string.snooze),
                snoozePendingIntent);

// Key for the string that's delivered in the action's intent.
private static final String KEY_TEXT_REPLY = "key_text_reply";

String replyLabel = getResources().getString(R.string.reply_label);
RemoteInput remoteInput = new RemoteInput.Builder(KEY_TEXT_REPLY)
        .setLabel(replyLabel)
        .build();

// Build a PendingIntent for the reply action to trigger.
PendingIntent replyPendingIntent =
        PendingIntent.getBroadcast(getApplicationContext(),
                conversation.getConversationId(),
                getMessageReplyIntent(conversation.getConversationId()),
                PendingIntent.FLAG_UPDATE_CURRENT);

// Create the reply action and add the remote input.
NotificationCompat.Action action =
        new NotificationCompat.Action.Builder(R.drawable.ic_reply_icon,
                getString(R.string.label), replyPendingIntent)
                .addRemoteInput(remoteInput)
                .build();

// Build the notification and add the action.
Notification newMessageNotification = new Notification.Builder(mContext, CHANNEL_ID)
        .setSmallIcon(R.drawable.ic_message)
        .setContentTitle(getString(R.string.title))
        .setContentText(getString(R.string.content))
        .addAction(action)
        .build();

// Issue the notification.
NotificationManagerCompat notificationManager = NotificationManagerCompat.from(this);
notificationManager.notify(notificationId, newMessageNotification);

private CharSequence getMessageText(Intent intent) {
    Bundle remoteInput = RemoteInput.getResultsFromIntent(intent);
    if (remoteInput != null) {
        return remoteInput.getCharSequence(KEY_TEXT_REPLY);
    }
    return null;
 }

// Build a new notification, which informs the user that the system
// handled their interaction with the previous notification.
Notification repliedNotification = new Notification.Builder(context, CHANNEL_ID)
        .setSmallIcon(R.drawable.ic_message)
        .setContentText(getString(R.string.replied))
        .build();

// Issue the new notification.
NotificationManagerCompat notificationManager = NotificationManagerCompat.from(this);
notificationManager.notify(notificationId, repliedNotification);