- A
[3,2,1]
Why wrong: Incorrect: sorting produces ascending order.
- B
Compilation fails
Why wrong: The code compiles successfully.
- C
[1,2,3]
Correct: after sorting, the list is in ascending order.
- D
[1,2]
Why wrong: Incorrect: all three elements are present.
- E
[1,3,2]
Why wrong: Incorrect: sorted list is [1,2,3].
Question 271 of 519
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.
Given: Set<Integer> set = new HashSet<>(List.of(1,2,3)); List<Integer> list = new ArrayList<>(set); Collections.sort(list); System.out.println(list); What is the output?
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
✓
[1,2,3]
The code creates a HashSet from a List of 1, 2, 3, then copies it into an ArrayList. HashSet does not guarantee order, but Collections.sort() sorts the list in natural ascending order (1, 2, 3). The output is [1,2,3], making option C correct.
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.
- ✗
[3,2,1]
Why it's wrong here
Incorrect: sorting produces ascending order.
- ✗
Compilation fails
Why it's wrong here
The code compiles successfully.
- ✓
[1,2,3]
Why this is correct
Correct: after sorting, the list is in ascending order.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
[1,2]
Why it's wrong here
Incorrect: all three elements are present.
- ✗
[1,3,2]
Why it's wrong here
Incorrect: sorted list is [1,2,3].
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume HashSet preserves insertion order (like LinkedHashSet) and thus expect unsorted output, forgetting that Collections.sort() explicitly sorts the list into ascending order.
Detailed technical explanation
How to think about this question
Under the hood, Collections.sort() uses a modified mergesort (TimSort) on the list's internal array, which is O(n log n) and stable. The HashSet constructor with a Collection copies elements in iteration order, which is unpredictable for HashSet (based on hash buckets), but sorting eliminates that unpredictability. In real-world scenarios, relying on HashSet order for sorted output is a common pitfall; always use TreeSet or explicit sorting when order matters.
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.
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FAQ
Questions learners often ask
What does this 1Z0-829 question test?
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: [1,2,3] — The code creates a HashSet from a List of 1, 2, 3, then copies it into an ArrayList. HashSet does not guarantee order, but Collections.sort() sorts the list in natural ascending order (1, 2, 3). The output is [1,2,3], making option C correct.
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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Last reviewed: Jun 25, 2026
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