Override with Inherited Caller

A subtle but powerful Java behavior: when a method inherited from a superclass calls another method (say, computeArea), Java looks up that called method on the actual object type, not the type that defined the caller.

If the subclass overrides computeArea, the inherited method ends up calling the subclass's version — even though the subclass never rewrote the caller itself.

On the AP exam, this is the heart of polymorphic-dispatch MCQs and is essential for understanding how Template Method-style designs work in AP-style class FRQs.

The setup

public class Shape {
    public double area() { return 0; }
    public String describe() {
        return "This shape has area " + area();
    }
}

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

Circle does NOT override describe() — only area().

What happens when you call describe on a Circle?

Circle c = new Circle(2);
System.out.println(c.describe());
// "This shape has area 12.566370614359172"

The inherited describe() runs (from Shape), but inside it, area() dispatches to Circle's version — because the actual object is a Circle.

Why this matters

The superclass doesn't need to know about its subclasses. As long as it calls an overridable method, subclasses can customize the behavior without rewriting the calling method.