how to build notification in android studio code example

Example 1: notification manager android

package com.example.notificationdemo;

import android.app.Activity;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.support.v4.app.NotificationCompat;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class MainActivity extends Activity {
   Button b1;
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);

      b1 = (Button)findViewById(R.id.button);
      b1.setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View v) {
            addNotification();
         }
      });
   }

   private void addNotification() {
      NotificationCompat.Builder builder =
         new NotificationCompat.Builder(this)
         .setSmallIcon(R.drawable.abc)
         .setContentTitle("Notifications Example")
         .setContentText("This is a test notification");

      Intent notificationIntent = new Intent(this, MainActivity.class);
      PendingIntent contentIntent = PendingIntent.getActivity(this, 0, notificationIntent,
         PendingIntent.FLAG_UPDATE_CURRENT);
      builder.setContentIntent(contentIntent);

      // Add as notification
      NotificationManager manager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
      manager.notify(0, builder.build());
   }
}

Example 2: create notification android

NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(yourContext.getApplicationContext(), "notify_001");
Intent ii = new Intent(yourContext.getApplicationContext(), YourMainActivty.class);
PendingIntent pendingIntent = PendingIntent.getActivity(yourContext, 0, ii, 0);

NotificationCompat.BigTextStyle bigText = new NotificationCompat.BigTextStyle();
bigText.bigText(notificationsTextDetailMode); //detail mode is the "expanded" notification
bigText.setBigContentTitle(notificationTitleDetailMode);
bigText.setSummaryText(usuallyAppVersionOrNumberOfNotifications); //small text under notification

mBuilder.setContentIntent(pendingIntent);
mBuilder.setSmallIcon(R.mipmap.ic_launcher); //notification icon
mBuilder.setContentTitle(notificationTitle); //main title
mBuilder.setContentText(notificationText); //main text when you "haven't expanded" the notification yet
mBuilder.setPriority(Notification.PRIORITY_MAX);
mBuilder.setStyle(bigText);

NotificationManager mNotificationManager = (NotificationManager) yourContext.getSystemService(Context.NOTIFICATION_SERVICE);

NotificationChannel channel = new NotificationChannel("notify_001",
                                                      "Channel human readable title",
                                                      NotificationManager.IMPORTANCE_DEFAULT);
if (mNotificationManager != null) {
  mNotificationManager.createNotificationChannel(channel);
}

if (mNotificationManager != null) {
  mNotificationManager.notify(0, mBuilder.build());
}