Java

Hi guys, 
I know how to write code in Java (basic and intermediate level). However, I have very little experience in looking at other peoples' code (experts) and understanding those. I know this is very much required in the industry. I would like to understand how architectures, e.g. MVC and design patterns are implemented by experts. 

Therefore, I am asking your recommendations for existing GITHUB projects for learning. I would like to look at a project with the following properties:

1.	Built with CORE java. It should have some sort of GUI (maybe JavaFX, which I know isn't CORE java).
2.	Followed some architecture and design patterns.
3.	It can be a game for example.
4.	It should have at least some documentation.

I have searched GUTHUB projects and too much choice has overwhelmed me. Please provide your valuable suggestion so that I can at least start somewhere.

Bye.   

I wanna create a library for sending notification to my android app but i don't know how it works and what kind of data i should give to the function in the class. this is my code for sending notification but i don't know how to put it in the class for using in another sections of the app. This code works in MainActivity

Intent intent = new Intent(context, MainActivity.class);
               PendingIntent contentIntent = PendingIntent.getActivity(context, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);

               NotificationCompat.Builder b = new NotificationCompat.Builder(context);

               b.setAutoCancel(true)
                       .setDefaults(Notification.DEFAULT_ALL)
                       .setWhen(System.currentTimeMillis())
                       .setSmallIcon(R.drawable.ic_launcher_background)
                       .setTicker("Hearty365")
                       .setContentTitle("Default notification")
                       .setContentText("Lorem ipsum dolor sit amet, consectetur adipiscing elit.")
                       .setDefaults(Notification.DEFAULT_LIGHTS | Notification.DEFAULT_SOUND)
                       .setContentIntent(contentIntent)
                       .setContentInfo("Info");


               NotificationManager notificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
               notificationManager.notify(1, b.build());

import java.io.IOException;
import java.net.URL;
import java.net.HttpURLConnection;
import java.lang.ClassNotFoundException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public final class TomSampleServletClient extends HttpServlet {
    
    @Override
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
        xxxx;
        xxxx;
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
    <servlet>
       <servlet-name>TomSampleServletClient</servlet-name>
       <servlet-class>TomSampleServletClient</servlet-class>
    </servlet>
    <servlet-mapping>
       <servlet-name>TomSampleServletClient</servlet-name>
       <url-pattern>/TomSampleServletClient</url-pattern>
    </servlet-mapping>
</web-app>