Unit 3 Cycle 1 Day 27: Inheritance Hierarchy Tracing

February 18, 2026

Unit 3 Foundation (Cycle 1) Day 27 of 28 Foundation

Inheritance Hierarchy Tracing

Section Mixed — Review: Inheritance

Key Concept

Inheritance hierarchy tracing involves following execution through multiple levels of superclass-subclass relationships. When three or more classes form a chain (e.g., Object → Vehicle → Car → Sedan), method resolution starts at the runtime type and moves up until a matching method is found. Constructor execution moves down from the top. The AP exam tests deep hierarchies where the answer depends on correctly identifying which class provides the method that actually executes.

Consider the following classes.

public class A { public String show() { return "A"; } } public class B extends A { public String show() { return "B"; } } public class C extends B { // does NOT override show() }

What does new C().show() return?

Answer: (B) "B"

C does not override show(). Java looks up the inheritance chain: C has no show(), B has show() returning "B". B's version is used.

Why Not the Others?

(A) B overrides A's show(). Java finds B's version before reaching A.

(C) C does not define show(), so there is no "C" to return.

(D) C inherits show() from B. No compile error.

Common Mistake

When a method is not overridden in the current class, Java searches up the inheritance chain. It uses the first matching method found, which is B's in this case.