Inheritance with extends and the super Keyword0%

Method Overriding and Dynamic Method Dispatch (Runtime Polymorphism)

Inheritance with extends and the super Keyword

Intermediate13 min read•Updated: 2026-10-22

🧬 Inheritance with extends and the super Keyword

Introduction

Inheritance allows a new class (subclass / child) to acquire fields and methods from an existing class (superclass / parent) using the extends keyword. Java supports Single Inheritance of classes (a class can only directly extend one superclass).

🦸 The `super` Keyword

The super keyword refers directly to the immediate parent class:

1
super(): Calls the parent constructor (must be the first line of the child constructor).
2
super.member: Accesses parent variables shadowed by child variables.
3
super.method(): Invokes parent method implementations from an overriding method.

💻 Full Code Demonstration

1// Superclass
2class Employee {
3    protected String name;
4    protected int id;
5    protected double baseSalary;
6 
7    public Employee(String name, int id, double salary) {
8        this.name = name;
9        this.id = id;
10        this.baseSalary = salary;
11    }
12 
13    public void display() {
14        System.out.printf("Employee #%d: %s | Base Salary: ₹%,.2f%n", id, name, baseSalary);
15    }
16}
17 
18// Subclass
19class Instructor extends Employee {
20    private String subjectSpecialization;
21 
22    public Instructor(String name, int id, double salary, String subject) {
23        super(name, id, salary); // Invokes Employee constructor
24        this.subjectSpecialization = subject;
25    }
26 
27    @Override
28    public void display() {
29        super.display(); // Reuses base display logic
30        System.out.println("Specialization: " + subjectSpecialization);
31    }
32}
33 
34public class InheritanceDemo {
35    public static void main(String[] args) {
36        Instructor prof = new Instructor("Er. Sumit Sharma", 101, 85000.0, "Java & Systems Architecture");
37        prof.display();
38    }
39}

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The java.lang.Object Class: toString(), equals(), and hashCode()	Method Overriding and Dynamic Method Dispatch (Runtime Polymorphism)

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Method Overriding and Dynamic Method Dispatch (Runtime Polymorphism)

Inheritance with extends and the super Keyword

Intermediate13 min read•Updated: 2026-10-22

Study Materials

🧬 Inheritance with extends and the super Keyword

Introduction

🦸 The `super` Keyword

The super keyword refers directly to the immediate parent class:

1
super(): Calls the parent constructor (must be the first line of the child constructor).
2
super.member: Accesses parent variables shadowed by child variables.
3
super.method(): Invokes parent method implementations from an overriding method.

💻 Full Code Demonstration

1// Superclass
2class Employee {
3    protected String name;
4    protected int id;
5    protected double baseSalary;
6 
7    public Employee(String name, int id, double salary) {
8        this.name = name;
9        this.id = id;
10        this.baseSalary = salary;
11    }
12 
13    public void display() {
14        System.out.printf("Employee #%d: %s | Base Salary: ₹%,.2f%n", id, name, baseSalary);
15    }
16}
17 
18// Subclass
19class Instructor extends Employee {
20    private String subjectSpecialization;
21 
22    public Instructor(String name, int id, double salary, String subject) {
23        super(name, id, salary); // Invokes Employee constructor
24        this.subjectSpecialization = subject;
25    }
26 
27    @Override
28    public void display() {
29        super.display(); // Reuses base display logic
30        System.out.println("Specialization: " + subjectSpecialization);
31    }
32}
33 
34public class InheritanceDemo {
35    public static void main(String[] args) {
36        Instructor prof = new Instructor("Er. Sumit Sharma", 101, 85000.0, "Java & Systems Architecture");
37        prof.display();
38    }
39}

Next Lesson

Method Overriding and Dynamic Method Dispatch (Runtime Polymorphism)

Continue learning with hands-on practice, examples, and exercises in the upcoming topic.

Related Lessons

Previous Lesson	Next Lesson
The java.lang.Object Class: toString(), equals(), and hashCode()	Method Overriding and Dynamic Method Dispatch (Runtime Polymorphism)

Practice Quiz

Test your understanding of this lesson with 1 questions. Each question has one correct answer.

Previous Next

🧬 Inheritance with extends and the super Keyword

Introduction

🦸 The super Keyword

💻 Full Code Demonstration

Method Overriding and Dynamic Method Dispatch (Runtime Polymorphism)

Related Lessons

Practice Quiz

Loading Page Content...

🧬 Inheritance with extends and the super Keyword

Introduction

🦸 The super Keyword

💻 Full Code Demonstration

Method Overriding and Dynamic Method Dispatch (Runtime Polymorphism)

Related Lessons

Practice Quiz

🦸 The `super` Keyword

🦸 The `super` Keyword