1Z0-811 Object-Oriented Programming Practice Question
A team is designing a system where a 'Report' class can be generated in different formats (PDF, Excel, HTML). They want to avoid modifying the Report class when adding new formats. Which OOP principle or pattern should they use?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Composition
Omposition (often implemented via the Strategy pattern), which allows the Report class to delegate format generation to separate strategy objects. This adheres to the Open/Closed Principle: the Report class is closed for modification but open for extension. Adding a new format only requires creating a new strategy class without altering the Report class. Option B (Composition) is correct. Option A (Method Overloading) is incorrect because it would require adding a new overloaded method for each format in the Report class, violating the goal of not modifying it. Option C (Inheritance) is incorrect because it would create a rigid hierarchy where each format is a subclass of Report, leading to tight coupling and difficulty in adding new formats without modifying existing code. Option D (Singleton) is incorrect because it ensures a single instance, which does not address the need for flexible format generation.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Method Overloading
Why it's wrong here
Overloading is compile-time and not suitable for runtime format selection.
- ✓
Composition
Why this is correct
Composing Report with a formatter interface allows adding formats without modifying Report.
- ✗
Inheritance
Why it's wrong here
Inheritance would require creating subclasses for each format, modifying Report if new formats are added.
- ✗
Singleton
Why it's wrong here
Singleton controls instantiation but does not support extensibility.
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