Advanced Coding & Software Engineering Program

Java super Keyword Tutorial with Real-Life Example

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Last Updated on: 12th Nov 2025 16:49:12 PM

Welcome to this beginner-friendly tutorial on the super keyword in Java! The super keyword is used in inheritance to refer to the immediate parent class. It helps access parent class members (variables, methods, and constructors) when they are hidden or overridden in the child class.

 

This tutorial uses a real-world project-based example — a Hospital Management System — to show how super is used in real software development.

 

What is the super Keyword?

In Java, the super keyword is used to refer to the immediate parent class. It helps when a subclass wants to access something (like variables, methods, or constructors) from its parent class that it has overridden or hidden.

 

super is a reference variable that refers to the immediate parent class object. It is used to:

1. Call parent class constructor

2. Access parent class method

3. Access parent class variable

 

Uses of super Keyword

Use	Syntax	Purpose
1. Call parent constructor	super() or super(args)	Initialize parent class fields
2. Call parent method	super.methodName()	Execute parent’s version
3. Access parent variable	super.variableName	Get parent’s field value

 

1. Using super to Access Parent Class Variable

class Animal {
    String name = "Animal";
}

class Dog extends Animal {
    String name = "Dog";

    void display() {
        System.out.println("Child class name: " + name);
        System.out.println("Parent class name: " + super.name);
    }
}

public class Main {
    public static void main(String[] args) {
        Dog obj = new Dog();
        obj.display();
    }
}

 

Output:

Child class name: Dog
Parent class name: Animal

 

Explanation:

• super.name refers to the parent class variable (Animal).

• name refers to the child class variable (Dog).

 

2. Using super to Call Parent Class Method & Constructor

class Course {
    Course() {
        System.out.println("Course is being created...");
    }

    void displayDetails() {
        System.out.println("This is a general course.");
    }
}

class JavaCourse extends Course {
    JavaCourse() {
        super(); // Calls Course constructor
        System.out.println("Java Course initialized successfully!");
    }

    void displayDetails() {
        super.displayDetails(); // Calls parent method
        System.out.println("This is a specialized Java Full Stack course.");
    }
}

public class Main {
    public static void main(String[] args) {
        JavaCourse jc = new JavaCourse();
        jc.displayDetails();
    }
}

 

Output:

Course is being created...
Java Course initialized successfully!
This is a general course.
This is a specialized Java Full Stack course.

 

Explanation:

• When super() is used inside a constructor, it must be the first statement.

• It calls the parent class constructor before executing the child class constructor.

 

Real-Time Project: Hospital Management System

Let’s build a Hospital App with:

• Person → Base class

• Doctor, Nurse, Patient → Subclasses

 

We’ll use super to reuse and extend parent behavior.

 

Step 1: Parent Class – Person.java

// Person.java
public class Person {
    protected String name;
    protected int age;
    protected String contact;

    // Parent constructor
    public Person(String name, int age, String contact) {
        this.name = name;
        this.age = age;
        this.contact = contact;
        System.out.println("[Person] Created: " + name);
    }

    // Parent method
    public void displayBasicInfo() {
        System.out.println("Name: " + name);
        System.out.println("Age: " + age);
        System.out.println("Contact: " + contact);
    }

    // Method to be overridden
    public void showRole() {
        System.out.println("Role: General Person");
    }
}

 

Step 2: Child Classes Using super

1. Doctor.java

public class Doctor extends Person {
    private String specialization;
    private String licenseNo;
    private double salary;

    // Use super() to call parent constructor
    public Doctor(String name, int age, String contact, 
                  String specialization, String licenseNo, double salary) {
        super(name, age, contact);  // Call parent constructor
        this.specialization = specialization;
        this.licenseNo = licenseNo;
        this.salary = salary;
        System.out.println("[Doctor] Assigned: " + specialization);
    }

    // Override parent method
    @Override
    public void showRole() {
        System.out.println("Role: Doctor");
    }

    // Use super.method() to extend parent behavior
    public void displayFullInfo() {
        super.displayBasicInfo();  // Call parent method
        System.out.println("Specialization: " + specialization);
        System.out.println("License: " + licenseNo);
        System.out.println("Salary: ₹" + salary);
    }
}

 

2. Nurse.java

public class Nurse extends Person {
    private String department;
    private int shiftHours;

    public Nurse(String name, int age, String contact, 
                 String department, int shiftHours) {
        super(name, age, contact);
        this.department = department;
        this.shiftHours = shiftHours;
        System.out.println("[Nurse] Assigned to: " + department);
    }

    @Override
    public void showRole() {
        System.out.println("Role: Nurse");
    }

    public void displayShift() {
        super.displayBasicInfo();  // Reuse parent
        System.out.println("Department: " + department);
        System.out.println("Shift: " + shiftHours + " hours");
    }
}

 

3. Patient.java

public class Patient extends Person {
    private String patientId;
    private String ailment;
    private String admittedDate;

    public Patient(String name, int age, String contact, 
                   String patientId, String ailment, String admittedDate) {
        super(name, age, contact);
        this.patientId = patientId;
        this.ailment = ailment;
        this.admittedDate = admittedDate;
        System.out.println("[Patient] Admitted for: " + ailment);
    }

    @Override
    public void showRole() {
        System.out.println("Role: Patient");
    }

    public void displayRecord() {
        super.displayBasicInfo();
        System.out.println("Patient ID: " + patientId);
        System.out.println("Ailment: " + ailment);
        System.out.println("Admitted: " + admittedDate);
    }
}

 

Step 3: Main App – HospitalManagement.java

// HospitalManagement.java
import java.util.ArrayList;
import java.util.List;

public class HospitalManagement {
    public static void main(String[] args) {
        System.out.println("HOSPITAL MANAGEMENT SYSTEM\n");

        // Create objects
        Doctor doc = new Doctor("Dr. Rajesh Kumar", 45, "9876543210",
                                "Cardiologist", "LIC-789", 250000);

        Nurse nurse = new Nurse("Anita Sharma", 32, "9123456789",
                                "ICU", 8);

        Patient patient = new Patient("Vikram Singh", 28, "9988776655",
                                      "P-1001", "Fever & Cough", "2025-04-05");

        System.out.println("\n" + "=".repeat(50));

        // Use overridden + super methods
        List<Person> staff = new ArrayList<>();
        staff.add(doc);
        staff.add(nurse);
        staff.add(patient);

        for (Person p : staff) {
            p.showRole();           // Runtime polymorphism
            if (p instanceof Doctor) {
                ((Doctor) p).displayFullInfo();
            } else if (p instanceof Nurse) {
                ((Nurse) p).displayShift();
            } else if (p instanceof Patient) {
                ((Patient) p).displayRecord();
            }
            System.out.println("-".repeat(30));
        }
    }
}

 

Output

HOSPITAL MANAGEMENT SYSTEM

[Person] Created: Dr. Rajesh Kumar
[Doctor] Assigned: Cardiologist
[Person] Created: Anita Sharma
[Nurse] Assigned to: ICU
[Person] Created: Vikram Singh
[Patient] Admitted for: Fever & Cough

==================================================
Role: Doctor
Name: Dr. Rajesh Kumar
Age: 45
Contact: 9876543210
Specialization: Cardiologist
License: LIC-789
Salary: ₹250000.0
------------------------------
Role: Nurse
Name: Anita Sharma
Age: 32
Contact: 9123456789
Department: ICU
Shift: 8 hours
------------------------------
Role: Patient
Name: Vikram Singh
Age: 28
Contact: 9988776655
Patient ID: P-1001
Ailment: Fever & Cough
Admitted: 2025-04-05
------------------------------

 

When to Use super?

Scenario	Use super
Parent and child have same variable name	super.name
Child wants to extend parent method	super.method()
Must initialize parent fields	super(args) in constructor

 

Rules & Best Practices

1. super() must be the first statement in constructor

2. Use @Override with super.method() for clarity

3. super cannot be used in static context

4. Always call super() if parent has no default constructor

// Valid
public Child() {
    super("default");  // First line
    // other code
}

// Invalid
public Child() {
    // some code
    super();  // COMPILE ERROR!
}

 

Real-Time Use Cases

System	super Usage
E-commerce	Product → Electronics → Mobile (call super.display())
HR System	Employee → Manager (reuse calculateSalary())
Game Engine	GameObject → Player, Enemy (call super.update())

 

Common Mistakes 

// Wrong: Missing super() when parent has parameterized constructor
class Parent {
    Parent(String x) { }
}
class Child extends Parent {  // ERROR if no super()
}

// Correct
class Child extends Parent {
    Child() {
        super("default");
    }
}

 

Summary

• super = Reference to parent class

• 3 Uses:

  1. super() → Call parent constructor

  2. super.method() → Call parent method

  3. super.var → Access parent variable

• Essential for code reuse and initialization

• Used in every real-world inheritance project

 

Key Points to Remember

✅ super refers to the immediate parent class only (not the grandparent).
✅ You can’t use super inside static methods.
✅ super() must be the first line in a constructor if used.
✅ If you don’t explicitly call super(), Java automatically calls the no-argument constructor of the parent class.

 

Project Tip:
In your Hospital App, use super in:

• Staff → Doctor, Nurse

• Billable → Consultation, Surgery

• User → Admin, Receptionist

 

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You now fully understand the super keyword with a real-world hospital system!
Keep practicing — happy coding!  

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