Object-Oriented Programming Basics

Duration: 7.0 min

This module delves into the foundational principles of Object-Oriented Programming (OOP) in Java, which is crucial for building robust and scalable applications. Understanding OOP concepts such as classes, objects, inheritance, and polymorphism will enable you to design software that is modular, reusable, and easy to maintain.

Classes and Objects

Visual Guide: This module includes diagrams and flowcharts. Check the course materials for detailed visualizations.

In Java, a class is a blueprint for creating objects. It encapsulates data for the object and methods to manipulate that data. An object is an instance of a class. Classes define the structure and behavior (methods) that the objects created from the class can use. This encapsulation helps in organizing code and managing complexity.

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

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

    // Methods
    public String getColor() {
        return color;
    }

    public String getModel() {
        return model;
    }
}

public class Main {
    public static void main(String[] args) {
        // Creating an object of Car
        Car myCar = new Car("Red", "Toyota");
        System.out.println("Car Model: " + myCar.getModel());
        System.out.println("Car Color: " + myCar.getColor());
    }
}

Car Model: Toyota
Car Color: Red

Inheritance

Inheritance is a mechanism where one class inherits the fields and methods of another class. This allows for code reusability and the creation of a hierarchical class structure. The class that is inherited from is called the superclass, and the class that inherits is called the subclass.

class Animal {
    void eat() {
        System.out.println("eating");
    }
}

class Dog extends Animal {
    void bark() {
        System.out.println("barking");
    }
}

public class Main {
    public static void main(String[] args) {
        Dog myDog = new Dog();
        myDog.eat();
        myDog.bark();
    }
}

eating
barking

💡 Tip: Remember to use the 'super' keyword to call the superclass constructor from the subclass constructor when you need to initialize inherited fields.

// Example 3
public class Example3 {
    public static void main(String[] args) {
        System.out.println("Example 3");
    }
}

Example 3

// Example 4
public class Example4 {
    public static void main(String[] args) {
        System.out.println("Example 4");
    }
}

Example 4

// Example 5
public class Example5 {
    public static void main(String[] args) {
        System.out.println("Example 5");
    }
}

Example 5

Learn more: https://docs.oracle.com/javase/tutorial/