Quick Answer
The correct approach to sort an int array in descending order is to first sort it in ascending order using Arrays.sort(arr) and then manually reverse the array. This works because Arrays.sort() arranges primitive ints from smallest to largest, and reversing that order gives you descending order. The other options fail because Arrays.parallelSort() also sorts ascending, Collections.reverseOrder() requires an array of objects like Integer, not primitives, and a custom comparator cannot be applied to primitive arrays in Java. On the Oracle Java Foundations 1Z0-811 exam, this question tests your understanding of the limitations of sorting primitives versus objects, and the common trap is assuming you can directly apply a reverse comparator to int[]. Remember the memory tip: sort ascending, then reverse—primitives need two steps, objects can do it in one.
This 1Z0-811 practice question tests your understanding of arrays and methods. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 wants to sort an array of primitive ints in descending order. Which approach will work without using third-party libraries?
Arrays.parallelSort(arr);
Why wrong: Sorts in ascending order, not descending.
Arrays.sort(arr, Collections.reverseOrder());
Why wrong: reverseOrder() requires an Object array, not primitive int[].
Arrays.sort(arr); // then reverse the array manually
Sorts ascending, then reversing yields descending order.
Arrays.sort(arr, (a,b) -> b - a);
Why wrong: Lambda comparator requires an Object array; cannot be used with int[].
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Arrays.sort(arr); // then reverse the array manually
Option C is correct because `Arrays.sort(int[])` sorts the array in ascending order, and then manually reversing the array yields descending order. The other options fail because `Arrays.parallelSort()` also sorts ascending, `Collections.reverseOrder()` requires an array of objects (not primitives), and a custom comparator cannot be used with primitive arrays in Java.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Arrays.parallelSort(arr);
Why it's wrong here
Sorts in ascending order, not descending.
Arrays.sort(arr, Collections.reverseOrder());
Why it's wrong here
reverseOrder() requires an Object array, not primitive int[].
Arrays.sort(arr); // then reverse the array manually
Why this is correct
Sorts ascending, then reversing yields descending order.
Related concept
Read the scenario before looking for a memorised answer.
Arrays.sort(arr, (a,b) -> b - a);
Why it's wrong here
Lambda comparator requires an Object array; cannot be used with int[].
Common exam traps
The trap here is that candidates assume `Arrays.sort()` with a comparator works on primitive arrays, but Java's type system prevents this because comparators require object types, leading to a compilation error for `int[]`.
Detailed technical explanation
Java's `Arrays.sort()` for primitives uses a dual-pivot quicksort algorithm (for `int[]`), which sorts in natural ascending order. To achieve descending order, you must either box the primitives into `Integer[]` and use `Arrays.sort(T[], Comparator)` or sort ascending and reverse manually. The manual reversal approach avoids boxing overhead and is efficient for large arrays, though it requires an extra pass over the array.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the 1Z0-811 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
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FAQ
Arrays and Methods — This question tests Arrays and Methods — Read the scenario before looking for a memorised answer..
The correct answer is: Arrays.sort(arr); // then reverse the array manually — Option C is correct because `Arrays.sort(int[])` sorts the array in ascending order, and then manually reversing the array yields descending order. The other options fail because `Arrays.parallelSort()` also sorts ascending, `Collections.reverseOrder()` requires an array of objects (not primitives), and a custom comparator cannot be used with primitive arrays in Java.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
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