Solution:Step 1: Understand abstract method requirementsAbstract methods must be implemented by concrete subclasses or the subclass must be abstract.Step 2: Analyze subclass behaviorOverriding concrete methods is allowed but does not satisfy abstract method implementation.Step 3: Compilation consequ

[Solved] A developer extends an abstract class that provides a concrete method and declares an abstract method. The subclass overrides the concrete method but does not implement the abstract method.... | OOP & Design Patterns

OOP & Design Patterns - Abstraction - Abstract Class vs Interface - When to Use Which

A developer extends an abstract class that provides a concrete method and declares an abstract method. The subclass overrides the concrete method but does not implement the abstract method. What is the outcome?

AThe subclass must be declared abstract or implement the abstract method to compile.

BThe subclass runtime throws an error when the abstract method is called.

CThe subclass inherits the abstract method implementation from the abstract class.

DThe subclass compiles successfully because it overrides the concrete method.

Step-by-Step Solution

Solution:

Step 1: Understand abstract method requirements
Abstract methods must be implemented by concrete subclasses or the subclass must be abstract.
Step 2: Analyze subclass behavior
Overriding concrete methods is allowed but does not satisfy abstract method implementation.
Step 3: Compilation consequences
Subclass without abstract method implementation must be abstract or compilation fails.
Final Answer:
Option A -> Option A
Quick Check:
Abstract methods require implementation or subclass must be abstract [OK]

Quick Trick: Abstract methods must be implemented or subclass declared abstract [OK]

Common Mistakes:

MISTAKES

Assuming overriding concrete methods suffices
Believing abstract methods have default implementations
Thinking runtime errors occur instead of compile errors

Trap Explanation:

PITFALL

Candidates confuse concrete method overrides with abstract method implementation requirements.

Interviewer Note:

CONTEXT

Checks understanding of abstract class inheritance rules and method implementation.

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Solution Trace

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What is the outcome?

Step 1: Understand abstract method requirements

Step 2: Analyze subclass behavior

Step 3: Compilation consequences

Final Answer:

Quick Check:

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