JavaCourse 2 of 2 · Java Mastery

Object-Oriented & Advanced Java

Classes, inheritance, interfaces, generics, and streams: the concepts behind real Java systems.

4 sessions
60 min each
Intermediate

Builds on Course 1
Browser editor or a JDK and VS Code
Certificate when you finish both courses

Course overview

What you'll learn

Classes and objects, constructors, private fields with getters and setters, toString, and static members, in a bank account class.
extends and super, overriding, one loop for a whole family of classes, and abstract classes, with animals and shapes.
Interfaces as contracts, your own checked and unchecked exceptions, and try-with-resources reading a file.
Your own generic class, lambdas, stream pipelines and Optional, ending in a small library system that uses the whole course.

Who this course is for

You finished Course 1, The Fundamentals, or already know what it covers.
You learn best by writing the code yourself, not by watching videos.
You want feedback on your own code, at your own pace, one hour at a time.
You would rather start in the browser than install tools first.

Course syllabus

4 sessions
24 blocks of 10 min
4 hours

Each session is one hour with the AI tutor and uses one credit. Sign in to start.

Session 1NextClasses, Objects & EncapsulationClasses and objects, constructors, private fields with getters and setters, toString, and static members, in a bank account class.
1. Welcome and your first class10 min
2. Constructors and this10 min
3. Encapsulation with private fields10 min
4. Getters, setters, toString and static members10 min
5. Mini project: the bank10 min
6. Final check and wrap-up10 min
Start session
Session 2Inheritance & Polymorphismextends and super, overriding, one loop for a whole family of classes, and abstract classes, with animals and shapes.
1. Welcome back and inheritance10 min
2. Overriding10 min
3. Polymorphism10 min
4. Abstract classes10 min
5. Mini project: a family of shapes10 min
6. Final check and wrap-up10 min
Start session
Session 3Interfaces & Exception DesignInterfaces as contracts, your own checked and unchecked exceptions, and try-with-resources reading a file.
1. Welcome back and interfaces10 min
2. Interfaces vs abstract classes10 min
3. Your own exceptions10 min
4. Reading a file with try-with-resources10 min
5. Mini project: a safe payroll10 min
6. Final check and wrap-up10 min
Start session
Session 4Generics, Streams & a Library SystemYour own generic class, lambdas, stream pipelines and Optional, ending in a small library system that uses the whole course.
1. Welcome back and your own generic class10 min
2. Lambdas10 min
3. Streams and Optional10 min
4. Capstone, part 1: the items10 min
5. Capstone, part 2: the catalog10 min
6. Final check and wrap-up10 min
Start session

How the tutor teaches

The same three rules in every session, from the first line of code to the last.

Practice, not videos

You write all of the code. The tutor reacts to what you actually typed, line by line.

Hints, not answers

A ladder from a light nudge to the solution, and only after you have made a real attempt.

Real output, never invented

Your code runs for real. The tutor reads what the machine showed, and trusts it.

Keep the momentum going

Where the other paths begin.

All courses

name = "Craftstack"
age = 29

print(f"{name} is {age}")
# Craftstack is 29

for ch in name:

PythonThe WorkbenchPython from Scratch · 4 sessions · Beginner

<header>
  <h1>Craftstack</h1>
  <nav>
    <a href="/">Home</a>
  </nav>
</header>

WebHTML & CSSThe Structure & StyleThe Front-End Foundation · 4 sessions · Beginner

SELECT students.name, courses.title
FROM enrollments
JOIN students ON enrollments.student_id = students.id
JOIN courses ON enrollments.course_id = courses.id
WHERE students.age >= 21
ORDER BY students.name;

SQLDatabases & SQL FundamentalsDatabases & SQL · 5 sessions · Beginner

Errors you may meet in this course

Java

Java NullPointerException: Cannot invoke ... because ... is null

What Java's NullPointerException means, how to read the message that says which value was null, and the four places beginners usually meet it, with the fix for each. With code you can run.

29 October 2026 · 6 min read

Frequently asked questions

What students ask before they start Object-Oriented & Advanced Java.

Do I need to install anything?

Not for this course. The editor in the page runs your code next to the chat. If you prefer, you can use a JDK and VS Code on your own computer.

What if I get stuck?

The tutor gives a ladder of hints, from a light nudge to the solution, and only after you have made a real attempt.

Do I keep my code?

Yes. In the editor in the page, your project is saved on the server for this course, continues in your next session on any device, and downloads as a .zip.

Do I get a certificate?

Yes, for the whole path. When you have finished all 2 courses of Java Mastery (this is Course 2), you get the Java Mastery certificate of completion with your name: a link anyone can check, one-click LinkedIn and a PDF. Your progress towards it is on your dashboard.

Do I need anything from before?

This course builds on Course 1, The Fundamentals. Take the sessions in order.

Meet the tutor in a free 20-minute session.

Twenty minutes with the tutor, right in your browser. No card, nothing to install.

Start the free trial

A session: the tutor's chat on the left, the code editor with a Java program and its output on the right