The answer is to define a Sensor interface and use dependency injection to pass sensor objects to the processor. This design achieves extensibility by programming to an interface rather than an implementation, allowing the SensorDataProcessor to accept any new sensor type that implements the Sensor contract without requiring code changes to the processor itself. On the Oracle Java Foundations 1Z0-811 exam, this question tests your understanding of loose coupling and polymorphism, two core principles of object-oriented design. A common trap is choosing subclassing, which still forces the processor to know about each concrete sensor class, or a static factory, which merely moves the coupling to another class. For the exam, remember the memory tip: "Inject the interface, not the instance" — if you see direct instantiation of concrete classes inside a processor, that is a red flag for poor extensibility.
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 developer is working on a Java application that processes sensor data. The code uses a class 'SensorDataProcessor' which directly instantiates specific sensor classes like 'TemperatureSensor' and 'PressureSensor' inside its methods. The team wants to make the system extensible to support new sensor types without modifying the processor class. Which design change best achieves this?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Define a Sensor interface and use dependency injection to pass sensor objects to the processor
Option B is correct because defining a Sensor interface and using dependency injection (e.g., passing sensor objects via constructor or setter) decouples the processor from concrete sensor classes. Option A is wrong because creating subclasses for each sensor would still require modifying the processor if new sensor types are added. Option C is wrong because a static factory still couples the processor to the factory. Option D is wrong because reflection is complex and not the best practice for this scenario.
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.
✗
Make SensorDataProcessor abstract and subclass it for each sensor
Why it's wrong here
This still requires a new subclass of the processor for each sensor type.
✗
Use a static factory method in SensorDataProcessor to create sensors
Why it's wrong here
The processor remains coupled to the factory, which must be updated for new sensors.
✗
Create a separate configuration file listing sensors and use reflection to instantiate them
Why it's wrong here
Reflection is error-prone and performance-heavy; dependency injection is cleaner.
✓
Define a Sensor interface and use dependency injection to pass sensor objects to the processor
Why this is correct
Dependency injection allows the processor to work with any Sensor implementation.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
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 a Sensor interface and use dependency injection to pass sensor objects to the processor — Option B is correct because defining a Sensor interface and using dependency injection (e.g., passing sensor objects via constructor or setter) decouples the processor from concrete sensor classes. Option A is wrong because creating subclasses for each sensor would still require modifying the processor if new sensor types are added. Option C is wrong because a static factory still couples the processor to the factory. Option D is wrong because reflection is complex and not the best practice for this scenario.
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.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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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