Classes & Objects
Understand what classes and objects are. Learn how to define a class and create object instances.
Classes & Objects is a free Java Academy lesson on CoddyKit. This is lesson 1 of 3. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Java Academy learning path, and your progress syncs across the web and the CoddyKit app. The Java Academy course includes 3 lessons in total.
What is a class?
Class: A template that defines data (fields) and actions (methods). Think of it as a blueprint.
What is an object?
Object: A specific instance of a class. Each object has its own copy of the fields defined in the class.
Analogy
Analogy: A class is like a cookie cutter, and objects are the cookies made with it. One cutter, many cookies.
Why classes and objects?
Classes and objects let us organize code, reuse structure, and model real-world entities. This is the foundation of OOP.
Steps to use
Step 1: Define a class with fields and methods. Step 2: Use the new keyword to create objects. Step 3: Access fields or call methods on the object.
Demo: class and object
Code demo: define a Dog class with fields, then create Dog objects and set their data. Each object has its own state.
public class Main {
// Define a simple class inside Main for demo
static class Dog {
String name;
int age;
}
public static void main(String[] args) {
// Create two objects of Dog
Dog d1 = new Dog();
d1.name = "Buddy";
d1.age = 3;
Dog d2 = new Dog();
d2.name = "Luna";
d2.age = 5;
// Print their info
System.out.println(d1.name + " is " + d1.age + " years old.");
System.out.println(d2.name + " is " + d2.age + " years old.");
}
}
Object check
Quick check: What is an object in Java?
Recap
Recap: Classes are templates; objects are instances. You define once, create many, and each has its own state.
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Frequently Asked Questions
Is the “Classes & Objects” lesson free?
Yes — the full text of “Classes & Objects” is free to read here on the web. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Java Academy course, upgrade to CoddyKit PRO. The Java Academy course includes 3 lessons in total.
What will I learn in “Classes & Objects”?
Understand what classes and objects are. Learn how to define a class and create object instances. You practise Java Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Java Academy?
No prior experience is required. Java Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 1 of 3.
How long does the “Classes & Objects” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Java Academy lesson?
Yes. Every Java Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Classes & Objects
- Fields, Methods, Constructors
- Encapsulation (getters/setters)