The correct answer is that the unmodifiable list reflects the addition because `Collections.unmodifiableList()` returns a dynamic view backed by the original list, not a static snapshot. When you wrap a mutable list with this method, the wrapper delegates all read operations to the underlying list, so any structural modification—such as adding an element—to the original list is immediately visible through the unmodifiable view. On the Oracle Certified Professional Java SE 17 Developer 1Z0-829 exam, this concept tests your understanding of the difference between an unmodifiable view and an immutable copy; a common trap is assuming `unmodifiableList()` creates a frozen copy like `List.copyOf()` does. Remember the memory tip: “View, not vault”—the wrapper is a window into the original list, not a sealed container.
1Z0-829 Working with Arrays and Collections Practice Question
This 1Z0-829 practice question tests your understanding of working with arrays and collections. 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 creates an unmodifiable list via Collections.unmodifiableList(originalList). Later, originalList is modified by adding an element. Which statement is true?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The unmodifiable list reflects the addition
D is correct because `Collections.unmodifiableList()` returns a view-backed unmodifiable list that reflects any changes made to the original list. The unmodifiable list does not create a snapshot; it wraps the original list, so modifications to the original are visible through the unmodifiable wrapper.
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.
✗
The unmodifiable list remains unchanged
Why it's wrong here
It reflects changes to the original.
✗
The unmodifiable list becomes inconsistent
Why it's wrong here
It remains consistent as a view.
✗
An UnsupportedOperationException is thrown
Why it's wrong here
Modifying the original does not affect the view's state directly; exception only on direct modification attempts.
✓
The unmodifiable list reflects the addition
Why this is correct
Unmodifiable wrapper is a view; changes to backing list are visible.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume `Collections.unmodifiableList()` creates an immutable copy, similar to `List.copyOf()`, but it actually creates a dynamic view that changes with the original list.
Detailed technical explanation
How to think about this question
Under the hood, `Collections.unmodifiableList()` returns an instance of `UnmodifiableList` (a static inner class) that stores a reference to the original list and delegates all read operations (e.g., `get()`, `size()`, `iterator()`) to that backing list. This means the unmodifiable list is not a snapshot; it is a live view. In real-world scenarios, this can lead to unexpected behavior if the original list is shared across threads without synchronization, as the unmodifiable wrapper provides no thread safety.
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.
TExam Day Tips
→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 1Z0-829 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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Working with Arrays and Collections — This question tests Working with Arrays and Collections — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The unmodifiable list reflects the addition — D is correct because `Collections.unmodifiableList()` returns a view-backed unmodifiable list that reflects any changes made to the original list. The unmodifiable list does not create a snapshot; it wraps the original list, so modifications to the original are visible through the unmodifiable wrapper.
What should I do if I get this 1Z0-829 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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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