Method Overriding & polymorphism

polymorphism means 'many forms.' It allows a child class to provide a specific implementation of a method defined in the parent class. This enables a single variable to refer to different object types and call the appropriate method. This is a foundational concept in enterprise application development that professional developers rely on daily. The explanations below are written to be beginner-friendly while covering the depth and nuance that comes from real-world Java experience. Take your time with each section and practice the examples

45 min•By Priygop Team•Last updated: Feb 2026

polymorphism in Action

Example

class Shape {
    String name;
    
    Shape(String name) {
        this.name = name;
    }
    
    // Method to be overridden
    double area() {
        return 0;
    }
    
    void describe() {
        System.out.println(name + " — Area: " + String.format("%.2f", area()));
    }
}

class Circle extends Shape {
    double radius;
    
    Circle(double radius) {
        super("Circle");
        this.radius = radius;
    }
    
    @Override
    double area() {
        return Math.PI * radius * radius;
    }
}

class Rectangle extends Shape {
    double width, height;
    
    Rectangle(double width, double height) {
        super("Rectangle");
        this.width = width;
        this.height = height;
    }
    
    @Override
    double area() {
        return width * height;
    }
}

class Triangle extends Shape {
    double base, height;
    
    Triangle(double base, double height) {
        super("Triangle");
        this.base = base;
        this.height = height;
    }
    
    @Override
    double area() {
        return 0.5 * base * height;
    }
}

public class PolymorphismDemo {
    public static void main(String[] args) {
        // polymorphism: parent type holds child objects
        Shape[] shapes = {
            new Circle(5),
            new Rectangle(4, 6),
            new Triangle(8, 3),
            new Circle(3)
        };
        
        System.out.println("=== Shape Areas ===");
        double totalArea = 0;
        for (Shape shape : shapes) {
            shape.describe();  // Calls the correct overridden method!
            totalArea += shape.area();
        }
        System.out.println("Total area: " + String.format("%.2f", totalArea));
    }
}

Try It Yourself: Employee Payroll

Try It Yourself: Employee PayrollJava

Java Editor

✓ ValidTab = 2 spaces

class Employee {
    String name;
    int id;
    
    Employee(String name, int id) {
        this.name = name;
        this.id = id;
    }
    
    double calculatePay() {
        return 0;
    }
    
    void printPaySlip() {
        System.out.println("ID: " + id + " | " + name + " | Pay: $" + String.format("%.2f", calculatePay()));
    }
}

class FullTimeEmployee extends Employee {
    double monthlySalary;
    
    FullTimeEmployee(String name, int id, double salary) {
        super(name, id);
        this.monthlySalary = salary;
    }
    
    @Override
    double calculatePay() {
        return monthlySalary;
    }
}

class PartTimeEmployee extends Employee {
    double hourlyRate;
    int hoursWorked;
    
    PartTimeEmployee(String name, int id, double rate, int hours) {
        super(name, id);
        this.hourlyRate = rate;
        this.hoursWorked = hours;
    }
    
    @Override
    double calculatePay() {
        return hourlyRate * hoursWorked;
    }
}

class Contractor extends Employee {
    double projectFee;
    
    Contractor(String name, int id, double fee) {
        super(name, id);
        this.projectFee = fee;
    }
    
    @Override
    double calculatePay() {
        return projectFee;
    }
}

public class PayrollDemo {
    public static void main(String[] args) {
        Employee[] staff = {
            new FullTimeEmployee("Alice", 101, 5000),
            new PartTimeEmployee("Bob", 102, 25, 80),
            new Contractor("Charlie", 103, 8000),
            new FullTimeEmployee("Diana", 104, 6000)
        };
        
        System.out.println("=== Monthly Payroll ===");
        double totalPayroll = 0;
        for (Employee emp : staff) {
            emp.printPaySlip();
            totalPayroll += emp.calculatePay();
        }
        System.out.println("Total Payroll: $" + String.format("%.2f", totalPayroll));
    }
}

class Employee {
    String name;
    int id;
    
    Employee(String name, int id) {
        this.name = name;
        this.id = id;
    }
    
    double calculatePay() {
        return 0;
    }
    
    void printPaySlip() {
        System.out.println("ID: " + id + " | " + name + " | Pay: $" + String.format("%.2f", calculatePay()));
    }
}

class FullTimeEmployee extends Employee {
    double monthlySalary;
    
    FullTimeEmployee(String name, int id, double salary) {
        super(name, id);
        this.monthlySalary = salary;
    }
    
    @Override
    double calculatePay() {
        return monthlySalary;
    }
}

class PartTimeEmployee extends Employee {
    double hourlyRate;
    int hoursWorked;
    
    PartTimeEmployee(String name, int id, double rate, int hours) {
        super(name, id);
        this.hourlyRate = rate;
        this.hoursWorked = hours;
    }
    
    @Override
    double calculatePay() {
        return hourlyRate * hoursWorked;
    }
}

class Contractor extends Employee {
    double projectFee;
    
    Contractor(String name, int id, double fee) {
        super(name, id);
        this.projectFee = fee;
    }
    
    @Override
    double calculatePay() {
        return projectFee;
    }
}

public class PayrollDemo {
    public static void main(String[] args) {
        Employee[] staff = {
            new FullTimeEmployee("Alice", 101, 5000),
            new PartTimeEmployee("Bob", 102, 25, 80),
            new Contractor("Charlie", 103, 8000),
            new FullTimeEmployee("Diana", 104, 6000)
        };
        
        System.out.println("=== Monthly Payroll ===");
        double totalPayroll = 0;
        for (Employee emp : staff) {
            emp.printPaySlip();
            totalPayroll += emp.calculatePay();
        }
        System.out.println("Total Payroll: $" + String.format("%.2f", totalPayroll));
    }
}

Output

Click ▶ Run to see the result

Edit the code on the left, then click Run

Java|80 lines|1886 chars|✓ Valid syntax

UTF-8

Quick Quiz: polymorphism

Method Overriding & polymorphism

45 min•By Priygop Team•Last updated: Feb 2026

polymorphism in Action

Example

class Shape {
    String name;
    
    Shape(String name) {
        this.name = name;
    }
    
    // Method to be overridden
    double area() {
        return 0;
    }
    
    void describe() {
        System.out.println(name + " — Area: " + String.format("%.2f", area()));
    }
}

class Circle extends Shape {
    double radius;
    
    Circle(double radius) {
        super("Circle");
        this.radius = radius;
    }
    
    @Override
    double area() {
        return Math.PI * radius * radius;
    }
}

class Rectangle extends Shape {
    double width, height;
    
    Rectangle(double width, double height) {
        super("Rectangle");
        this.width = width;
        this.height = height;
    }
    
    @Override
    double area() {
        return width * height;
    }
}

class Triangle extends Shape {
    double base, height;
    
    Triangle(double base, double height) {
        super("Triangle");
        this.base = base;
        this.height = height;
    }
    
    @Override
    double area() {
        return 0.5 * base * height;
    }
}

public class PolymorphismDemo {
    public static void main(String[] args) {
        // polymorphism: parent type holds child objects
        Shape[] shapes = {
            new Circle(5),
            new Rectangle(4, 6),
            new Triangle(8, 3),
            new Circle(3)
        };
        
        System.out.println("=== Shape Areas ===");
        double totalArea = 0;
        for (Shape shape : shapes) {
            shape.describe();  // Calls the correct overridden method!
            totalArea += shape.area();
        }
        System.out.println("Total area: " + String.format("%.2f", totalArea));
    }
}

Try It Yourself: Employee Payroll

Try It Yourself: Employee PayrollJava

Java Editor

✓ ValidTab = 2 spaces

class Employee {
    String name;
    int id;
    
    Employee(String name, int id) {
        this.name = name;
        this.id = id;
    }
    
    double calculatePay() {
        return 0;
    }
    
    void printPaySlip() {
        System.out.println("ID: " + id + " | " + name + " | Pay: $" + String.format("%.2f", calculatePay()));
    }
}

class FullTimeEmployee extends Employee {
    double monthlySalary;
    
    FullTimeEmployee(String name, int id, double salary) {
        super(name, id);
        this.monthlySalary = salary;
    }
    
    @Override
    double calculatePay() {
        return monthlySalary;
    }
}

class PartTimeEmployee extends Employee {
    double hourlyRate;
    int hoursWorked;
    
    PartTimeEmployee(String name, int id, double rate, int hours) {
        super(name, id);
        this.hourlyRate = rate;
        this.hoursWorked = hours;
    }
    
    @Override
    double calculatePay() {
        return hourlyRate * hoursWorked;
    }
}

class Contractor extends Employee {
    double projectFee;
    
    Contractor(String name, int id, double fee) {
        super(name, id);
        this.projectFee = fee;
    }
    
    @Override
    double calculatePay() {
        return projectFee;
    }
}

public class PayrollDemo {
    public static void main(String[] args) {
        Employee[] staff = {
            new FullTimeEmployee("Alice", 101, 5000),
            new PartTimeEmployee("Bob", 102, 25, 80),
            new Contractor("Charlie", 103, 8000),
            new FullTimeEmployee("Diana", 104, 6000)
        };
        
        System.out.println("=== Monthly Payroll ===");
        double totalPayroll = 0;
        for (Employee emp : staff) {
            emp.printPaySlip();
            totalPayroll += emp.calculatePay();
        }
        System.out.println("Total Payroll: $" + String.format("%.2f", totalPayroll));
    }
}

Output

Click ▶ Run to see the result

Edit the code on the left, then click Run

Java|80 lines|1886 chars|✓ Valid syntax

UTF-8

Method Overriding & polymorphism

polymorphism in Action

Try It Yourself: Employee Payroll

Quick Quiz: polymorphism

Topics in This Module

Method Overriding & polymorphism

polymorphism in Action

Try It Yourself: Employee Payroll

Quick Quiz: polymorphism

Topics in This Module