Inheritance

Welcome back! Now that you have a solid understanding of classes and objects in Java, it's time to build on that knowledge by exploring inheritance. Consider it a natural progression in our journey into object-oriented programming (OOP).

Inheritance allows you to create a new class based on an existing class. By using inheritance, you can reuse code, add new features, and make your programs easier to manage and understand. Let's dive in and see what it's all about.

In this lesson, you'll understand how to use inheritance in Java. We'll cover:

1. What Inheritance Is
2. How to Implement Inheritance in Java
3. Why Inheritance Is Beneficial

You'll also learn about chaining inheritance and how to manage multiple inheritance using interfaces.

Inheritance is a way to establish a relationship between a new class (derived class) and an existing class (base class). The derived class inherits properties and behaviors (methods) from the base class. To better understand this concept, we'll use an example involving a Person class as the base class and a Student class as the derived class. This example will help demonstrate how properties and methods are inherited from the base class and how additional features can be added to the derived class.

Let’s start by defining a Person class, which will act as the base class in our example:

// Define the base class Person with name and age attributes
class Person {
    private String name;
    private int age;

    // Constructor to initialize name and age
    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    // Display method to show name and age
    public void display() {
        System.out.println("Name: " + name + ", Age: " + age);
    }
}

In this snippet, the Person class is defined with private attributes name and age. It also includes a constructor to initialize these attributes and a display method to print the details.

Now, let’s create a Student class that inherits from the Person class:

// Define the derived class Student, inheriting from Person
class Student extends Person {
    private String major;

    // Constructor to initialize name, age of the base class, and the major of the student
    public Student(String name, int age, String major) {
        super(name, age);
        this.major = major;
    }

    // Method to display major of the student
    public void displayMajor() {
        System.out.println("Major: " + major);
    }
}

In the Student class, we use the extends keyword to inherit from Person. The Student class reuses the name and age attributes from the Person class, and it adds a new attribute, major. The constructor uses the super keyword to call the base class constructor and initialize the inherited properties. The Student class also adds a displayMajor method to show the student’s major.