Quick Answer
The answer is that an UnsupportedOperationException is thrown at runtime. This occurs because the Arrays.asList() method returns a fixed-size list backed directly by the original array, meaning the list’s size is immutable and cannot be structurally modified. Any attempt to call add() or remove() on this list triggers the exception, as the underlying array cannot be resized. On the Oracle Certified Professional Java SE 17 Developer 1Z0-829 exam, this is a classic trap designed to test your understanding of the distinction between fixed-size lists and fully mutable collections like ArrayList. The exam often presents this scenario in a multiple-choice question where candidates mistakenly assume Arrays.asList() behaves like a regular List. A reliable memory tip: think of Arrays.asList() as a “view” of the array—you can change elements, but you cannot change the number of slots.
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.
Consider: List<String> list = Arrays.asList("A", "B", "C"); list.add("D"); What is the result?
An ArrayIndexOutOfBoundsException is thrown
Why wrong: Exception type is UnsupportedOperationException.
The list becomes [A, B, C, D]
Why wrong: Cannot add element to fixed-size list.
A ClassCastException is thrown
Why wrong: No casting issue.
An UnsupportedOperationException is thrown
Arrays.asList returns fixed-size list.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
An UnsupportedOperationException is thrown
The `Arrays.asList()` method returns a fixed-size list backed by the specified array. This list does not support structural modification operations like `add()` or `remove()`. Calling `add()` on such a list throws an `UnsupportedOperationException` at runtime.
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.
An ArrayIndexOutOfBoundsException is thrown
Why it's wrong here
Exception type is UnsupportedOperationException.
The list becomes [A, B, C, D]
Why it's wrong here
Cannot add element to fixed-size list.
A ClassCastException is thrown
Why it's wrong here
No casting issue.
An UnsupportedOperationException is thrown
Why this is correct
Arrays.asList returns fixed-size list.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates confuse `Arrays.asList()` with `new ArrayList<>(Arrays.asList(...))`, assuming the returned list is a regular mutable `ArrayList`, but the exam tests the fixed-size behavior of the wrapper list.
Detailed technical explanation
Under the hood, `Arrays.asList()` returns an instance of `java.util.Arrays$ArrayList`, a private inner class that extends `AbstractList` and overrides `set()` but not `add()` or `remove()`, so those methods inherit the default throwing behavior from `AbstractList`. This design ensures the list remains a view of the original array, preventing structural changes that would break the array's fixed length. In real-world scenarios, developers often mistakenly use `Arrays.asList()` when they need a fully mutable `ArrayList`, leading to this runtime exception.
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 1Z0-829 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
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FAQ
Working with Arrays and Collections — This question tests Working with Arrays and Collections — Read the scenario before looking for a memorised answer..
The correct answer is: An UnsupportedOperationException is thrown — The `Arrays.asList()` method returns a fixed-size list backed by the specified array. This list does not support structural modification operations like `add()` or `remove()`. Calling `add()` on such a list throws an `UnsupportedOperationException` at runtime.
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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