Inheritance

Definition

Inheritance lets a class reuse and extend another class with extends. The child class gets the parent's fields and methods and can add new ones or change existing ones. Use it for a true "is-a" relationship.

Example code

A manager is an employee with extras

class Employee {
    protected final String name;
    protected final int salary;

    Employee(String name, int salary) {
        this.name = name;
        this.salary = salary;
    }

    int yearlyPay() { return salary * 12; }
}

class Manager extends Employee {
    private final int bonus;

    Manager(String name, int salary, int bonus) {
        super(name, salary);             // reuse the parent's constructor
        this.bonus = bonus;
    }

    @Override
    int yearlyPay() { return super.yearlyPay() + bonus; }   // change inherited behaviour
}

class Demo {
    public static void main(String[] args) {
        Employee dev = new Employee("Asha", 5_000);
        Manager lead = new Manager("Ravi", 7_000, 10_000);
        System.out.println(dev.name + " earns " + dev.yearlyPay());
        System.out.println(lead.name + " earns " + lead.yearlyPay());
    }
}

// Output:
// Asha earns 60000
// Ravi earns 94000