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Object-Oriented Programming (OOP) is a programming paradigm that uses "objects" to design applications and computer programs. It utilizes several key concepts such as classes, objects, inheritance, polymorphism, encapsulation, and abstraction. This module will introduce you to these fundamental concepts and how they are implemented in Java.

Key Concepts of OOP

Classes and Objects
- Class: A blueprint for creating objects. It defines a datatype by bundling data and methods that work on the data into one single unit.
- Object: An instance of a class. It is created from a class and can use the methods and properties defined in the class.
Inheritance
- A mechanism where one class acquires the properties (fields) and behaviors (methods) of another class. It provides a way to reuse code and establish a natural hierarchy.
Polymorphism
- The ability of a single function or method to work in different ways based on the object it is acting upon. It allows methods to do different things based on the object it is acting upon.
Encapsulation
- The bundling of data with the methods that operate on that data. It restricts direct access to some of an object's components, which can prevent the accidental modification of data.
Abstraction
- The concept of hiding the complex implementation details and showing only the necessary features of an object. It helps in reducing programming complexity and effort.

Practical Example

Let's start with a simple example to illustrate these concepts.

Step 1: Define a Class

// Define a class named 'Car'
public class Car {
    // Fields (attributes)
    private String color;
    private String model;
    private int year;

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

    // Method to display car details
    public void displayDetails() {
        System.out.println("Car Model: " + model);
        System.out.println("Car Color: " + color);
        System.out.println("Car Year: " + year);
    }
}

Step 2: Create an Object

public class Main {
    public static void main(String[] args) {
        // Create an object of the Car class
        Car myCar = new Car("Red", "Toyota", 2020);
        
        // Call the method to display car details
        myCar.displayDetails();
    }
}

Explanation

Class Definition: The Car class is defined with three fields: color, model, and year. It also has a constructor to initialize these fields and a method displayDetails to print the car's details.
Object Creation: In the Main class, an object myCar of the Car class is created using the constructor. The displayDetails method is then called on this object to print the car's details.

Exercises

Exercise 1: Create a Class and Object

Define a class named Person with the following fields: name, age, and gender.
Create a constructor to initialize these fields.
Add a method displayInfo to print the person's details.
Create an object of the Person class in the Main class and call the displayInfo method.

Solution

public class Person {
    private String name;
    private int age;
    private String gender;

    public Person(String name, int age, String gender) {
        this.name = name;
        this.age = age;
        this.gender = gender;
    }

    public void displayInfo() {
        System.out.println("Name: " + name);
        System.out.println("Age: " + age);
        System.out.println("Gender: " + gender);
    }
}

public class Main {
    public static void main(String[] args) {
        Person person = new Person("Alice", 30, "Female");
        person.displayInfo();
    }
}

Exercise 2: Implement Inheritance

Define a class Animal with a method makeSound.
Create a subclass Dog that inherits from Animal and overrides the makeSound method to print "Bark".
Create an object of the Dog class and call the makeSound method.

Solution

class Animal {
    public void makeSound() {
        System.out.println("Some sound...");
    }
}

class Dog extends Animal {
    @Override
    public void makeSound() {
        System.out.println("Bark");
    }
}

public class Main {
    public static void main(String[] args) {
        Dog dog = new Dog();
        dog.makeSound(); // Output: Bark
    }
}

Summary

In this section, we introduced the fundamental concepts of Object-Oriented Programming (OOP) in Java. We covered:

Classes and Objects: The basic building blocks of OOP.
Inheritance: A way to reuse code and establish a hierarchy.
Polymorphism: The ability of methods to do different things based on the object.
Encapsulation: Bundling data and methods to restrict access.
Abstraction: Hiding complex details to reduce complexity.

In the next section, we will delve deeper into classes and objects, exploring more advanced features and best practices.

Introduction to OOP

Key Concepts of OOP

Practical Example

Step 1: Define a Class

Step 2: Create an Object

Explanation

Exercises

Exercise 1: Create a Class and Object

Solution

Exercise 2: Implement Inheritance

Solution

Summary

Java Programming Course

Module 1: Introduction to Java

Module 2: Control Flow

Module 3: Object-Oriented Programming

Module 4: Advanced Object-Oriented Programming

Module 5: Data Structures and Collections

Module 6: Exception Handling

Module 7: File I/O

Module 8: Multithreading and Concurrency

Module 9: Networking

Module 10: Advanced Topics

Module 11: Java Frameworks and Libraries

Module 12: Building Real-World Applications