Stateful Override Adding to Super

When a subclass introduces a new instance variable that contributes to a computation, the cleanest override delegates the inherited part to super.method() and adds the subclass's own field on top.

This keeps each class's responsibilities clean: the parent manages its own fields; the subclass manages its own field plus the combining logic.

On the AP exam, this pattern is the most common version of inheritance FRQ scoring — typically getTotalPay = super.getTotalPay + commission or similar.

Setup

public class Employee {
    private double salary;
    public Employee(double s) { salary = s; }
    public double getTotalPay() { return salary; }
}

public class SalesEmployee extends Employee {
    private double commission;
    public SalesEmployee(double s, double c) {
        super(s);
        commission = c;
    }
    @Override
    public double getTotalPay() {
        return super.getTotalPay() + commission;
    }
}

The Employee class never knew about commission — and doesn't have to. The SalesEmployee adds its own field and combines it in the override.

Why this respects encapsulation

The subclass can't read salary directly because it's private to Employee. But it doesn't need to: super.getTotalPay() returns the value that depends on salary.

Mutators of subclass state

The subclass can add its own setter for commission without affecting the inherited salary handling.