Java Classes and Objects: Foundation of Object-Oriented Programming

Learn about Java's object-oriented programming (OOP) paradigm, where everything is structured around classes and objects. Discover how classes define attributes and methods, and how objects represent real-world entities like a car, with properties like weight and color, and actions like drive and brake.

Java Classes and Objects

Java is an object-oriented programming language where everything is associated with classes and objects, each having attributes and methods. For example, in real life, a car is an object with attributes like weight and color, and methods like drive and brake.

Create a Class

To create a class in Java, use the keyword class:

public class Main {
int x = 5;
}
    

Create an Object

In Java, an object is created from a class. Once a class like Main is created, objects can be instantiated:

public class Main {
int x = 5;

public static void main(String[] args) {
Main myObj = new Main();
System.out.println(myObj.x);
}
}
    

5
    

Multiple Objects

You can create multiple objects of the same class:

public class Main {
int x = 5;

public static void main(String[] args) {
Main myObj1 = new Main();  // Object 1
Main myObj2 = new Main();  // Object 2
System.out.println(myObj1.x);
System.out.println(myObj2.x);
}
}
    

Using Multiple Classes

You can create objects of a class and access them from another class for better organization:

// File: Main.java
public class Main {
int x = 5;
}

// File: Second.java
class Second {
public static void main(String[] args) {
Main myObj = new Main();
System.out.println(myObj.x);
}
}
    

Ensure the Java file names match the class names for proper compilation and execution.