Question 507 of 481
1Z0-811 Object-Oriented Programming Practice Question
Which design principle is violated by making all fields public in a class?
⚠ Common exam trap
Oracle often tests the distinction between OOP principles by presenting a scenario that seems to involve inheritance or abstraction, but the core violation is always about data hiding and controlled access—candidates mistakenly choose 'abstraction' because they confuse hiding implementation details with hiding data fields.
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
✓
Encapsulation
Making all fields public violates the principle of encapsulation, which requires that an object's internal state be hidden from external access and only modifiable through controlled methods (getters/setters). In Java, public fields allow any class to directly read or modify the field, breaking data integrity and the ability to enforce invariants. Encapsulation is a core OOP concept that protects the internal representation of an object.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Inheritance
Why it's wrong here
Inheritance is about code reuse; public fields don't directly break it.
- ✗
Abstraction
Why it's wrong here
Abstraction hides implementation details; public fields expose them but abstraction is broader.
- ✓
Encapsulation
Why this is correct
Encapsulation hides internal data; public fields expose it.
- ✗
Polymorphism
Why it's wrong here
Polymorphism relates to method behavior, not field access.
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Last reviewed: Jun 30, 2026
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