Question 252 of 513
1Z0-829 Working with Arrays and Collections Practice Question
Given: TreeSet<Integer> ts = new TreeSet<>(Comparator.reverseOrder()); ts.add(10); ts.add(5); ts.add(20); ts.add(15); System.out.println(ts.first()); What is the result?
⚠ Common exam trap
Watch out — candidates often assume `first()` returns the first element added or the largest element in a reversed set, rather than understanding it always returns the smallest element according to the set's comparator.
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
✓
5
`TreeSet` with `Comparator.reverseOrder()` sorts elements in descending order (20, 15, 10, 5). The `first()` method returns the smallest element according to the comparator, which in descending order is the last element in the natural order, i.e., 5.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
20
Why it's wrong here
This is the last element, not first.
- ✗
15
Why it's wrong here
Not the first element.
- ✓
5
Why this is correct
Correct; first() returns the least element in reversed order.
- ✗
10
Why it's wrong here
Not the first element.
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Last reviewed: Jun 11, 2026
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