Java Classes and Objects

1. Introduction

In Java, classes and objects are fundamental to object-oriented programming. A class serves as a blueprint for creating objects, encapsulating data for the object and methods to manipulate that data.

2. Key Concepts

• **Class:** A template for creating objects, defining their properties and behaviors.
• **Object:** An instance of a class that contains state and behavior defined by the class.
• **Encapsulation:** Bundling the data (attributes) and methods (functions) that operate on the data into a single unit.
• **Inheritance:** Mechanism where a new class can inherit properties and methods from an existing class.
• **Polymorphism:** The ability to present the same interface for different underlying forms (data types).

3. Creating Classes

To create a class in Java, use the class keyword followed by the class name. Class names should start with an uppercase letter.

public class Car {
    // Attributes
    private String color;
    private String model;

    // Constructor
    public Car(String color, String model) {
        this.color = color;
        this.model = model;
    }

    // Method
    public void displayInfo() {
        System.out.println("Car model: " + model + ", Color: " + color);
    }
}

4. Creating Objects

Objects are created using the new keyword followed by the class constructor.

public class Main {
    public static void main(String[] args) {
        // Creating an object of the Car class
        Car myCar = new Car("Red", "Toyota");
        myCar.displayInfo();
    }
}

5. Best Practices

• Use meaningful class and method names.
• Keep class responsibilities single; a class should have one reason to change.
• Encapsulate fields and expose them through getters and setters.
• Use constructors to initialize object state.
• Document your classes and methods for better maintainability.

6. FAQ