Given a class hierarchy where class D inherits from B and C, and both B and C inherit from A, which line in the following pseudocode is the subtle bug causing the Diamond Problem to manifest incorrectly?

medium🐞 Bug Identification Q7 of Q15

OOP & Design Patterns - Inheritance - Types, Method Resolution Order & Diamond Problem

Given a class hierarchy where class D inherits from B and C, and both B and C inherit from A, which line in the following pseudocode is the subtle bug causing the Diamond Problem to manifest incorrectly? 1: class A { method foo() } 2: class B extends A { override foo() } 3: class C extends A { override foo() } 4: class D extends B, C { no override }

ALine 1: A's foo() is not marked virtual/overridable

BLine 2: B overrides foo() without calling super.foo()

CLine 3: C overrides foo() without calling super.foo()

DLine 4: D does not override foo(), causing ambiguity

Step-by-Step Solution

Solution:

Step 1: Identify diamond problem cause
Diamond problem arises when subclass inherits multiple conflicting overrides without resolution.
Step 2: Analyze lines
Lines 2 and 3 override foo(), but line 4 does not override or resolve ambiguity, causing the problem.
Step 3: Other lines
Line 1 is base method, virtualness depends on language; lines 2 and 3 overriding is normal.
Final Answer:
Option D -> Option D
Quick Check:
D must override to resolve ambiguity [OK]

Quick Trick: Subclass must override to resolve diamond ambiguity [OK]

Common Mistakes:

MISTAKES

Blaming base class for diamond problem
Thinking overrides without super calls cause diamond
Assuming no override is safe

Trap Explanation:

PITFALL

Candidates often miss that subclass must explicitly resolve conflicting inherited methods.

Interviewer Note:

CONTEXT

Tests ability to spot subtle inheritance bugs causing diamond issues.

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More OOP & Design Patterns Quizzes

Given a class hierarchy where class D inherits from B and C, and both B and C inherit from A, which line in the following pseudocode is the subtle bug causing the Diamond Problem to manifest incorrectly?

Step 1: Identify diamond problem cause

Step 2: Analyze lines

Step 3: Other lines

Final Answer:

Quick Check:

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