The correct answer is to define an interface Discountable with a method calculateDiscount() and have each product class implement it. This approach adheres to the Open/Closed Principle by allowing the system to extend behavior for new product types—such as adding a new Food subclass—without modifying any existing discount calculation logic. In the context of the Oracle Java Foundations 1Z0-811 exam, this question tests your understanding of polymorphism and interface-based design as a means to achieve OCP, a common topic in object-oriented programming sections. A frequent trap is choosing a solution that uses a switch statement or a conditional chain, which violates OCP by requiring edits to a central method each time a new type appears. Remember the memory tip: "Interface for extension, switch for destruction"—if you see a switch or if-else chain on type, it’s likely breaking OCP.
1Z0-811 Object-Oriented Programming Practice Question
This 1Z0-811 practice question tests your understanding of object-oriented programming. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A team is developing a large-scale e-commerce platform using Java. They have a class hierarchy: Product (abstract), Electronics, Clothing, Food. Each product has a discount method that applies different logic. The team notices that whenever a new product type is added, they must modify the existing discount calculation logic in multiple places, leading to high maintenance costs. They want to refactor to follow the Open/Closed Principle. Which approach should they take?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Define an interface Discountable with a method calculateDiscount() and have each product class implement it
Option A is correct because defining an interface Discountable with a calculateDiscount() method and having each product class implement it allows adding new product types without modifying existing code. Option B is wrong because it violates OCP by requiring changes to a switch statement. Option C is wrong because it also requires modification when new types are added. Option D is wrong because it uses reflection unnecessarily and still requires changes to map types.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Define an interface Discountable with a method calculateDiscount() and have each product class implement it
Why this is correct
This follows OCP: new products implement the interface, no existing code changes.
Related concept
Read the scenario before looking for a memorised answer.
✗
Create a single discount method in Product that uses if-else checks on type
Why it's wrong here
Adding a new product type requires modifying the if-else chain.
✗
Remove the discount method and handle it externally using reflection
Why it's wrong here
Reflection is fragile and still requires mapping new types to discount logic.
✗
Use a switch statement in a utility class to handle all product types
Why it's wrong here
This violates OCP because new product types require modifying the switch.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 1Z0-811 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which 1Z0-811 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Object-Oriented Programming — This question tests Object-Oriented Programming — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Define an interface Discountable with a method calculateDiscount() and have each product class implement it — Option A is correct because defining an interface Discountable with a calculateDiscount() method and having each product class implement it allows adding new product types without modifying existing code. Option B is wrong because it violates OCP by requiring changes to a switch statement. Option C is wrong because it also requires modification when new types are added. Option D is wrong because it uses reflection unnecessarily and still requires changes to map types.
What should I do if I get this 1Z0-811 question wrong?
Identify which 1Z0-811 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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