This 1Z0-829 practice question tests your understanding of working with arrays and collections. 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.
Given: var list = List.of("A", "B", "C"); list.set(0, "Z"); What is the result?
An ArrayIndexOutOfBoundsException is thrown
Why wrong: Index is valid; exception type is different.
An UnsupportedOperationException is thrown
List.of returns an unmodifiable list.
The code does not compile because var cannot be used with List.of
Why wrong: var is allowed for local variables.
The list is modified to [Z, B, C]
Why wrong: Immutable list cannot be modified.
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 `List.of()` method returns an immutable list, meaning its elements cannot be added, removed, or replaced. Calling `set()` on an immutable list throws an `UnsupportedOperationException` at runtime, which is why option B is correct.
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
Index is valid; exception type is different.
An UnsupportedOperationException is thrown
Why this is correct
List.of returns an unmodifiable list.
Related concept
Read the scenario before looking for a memorised answer.
The code does not compile because var cannot be used with List.of
Why it's wrong here
var is allowed for local variables.
The list is modified to [Z, B, C]
Why it's wrong here
Immutable list cannot be modified.
Common exam traps
The trap here is that candidates often assume `List.of()` returns a mutable list similar to `new ArrayList<>()`, but it actually returns an immutable list, and the `set()` method will throw an `UnsupportedOperationException` at runtime.
Detailed technical explanation
`List.of()` was introduced in Java 9 and returns an unmodifiable list backed by a fixed-size internal array. Any mutating operation like `set()`, `add()`, or `remove()` triggers an `UnsupportedOperationException`. Under the hood, the implementation delegates to `AbstractList`'s `set()` method, which throws this exception unless overridden. This is a common pattern for creating immutable collections in modern Java.
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
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 — study guide chapter
Learn the concepts, then practise the questions
Working with Arrays and Collections practice questions
Targeted practice on this topic area only
All 1Z0-829 questions
509 questions across all exam domains
Oracle Certified Professional Java SE 17 Developer 1Z0-829 study guide
Full concept coverage aligned to exam objectives
1Z0-829 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Practise 1Z0-829 questions linked to Handling Date, Time, Text, Numeric and Boolean Values.
Practise 1Z0-829 questions linked to Controlling Program Flow.
Practise 1Z0-829 questions linked to Utilizing Java Object-Oriented Approach.
Practise 1Z0-829 questions linked to Handling Exceptions.
Practise 1Z0-829 questions linked to Working with Arrays and Collections.
Practise 1Z0-829 questions linked to Working with Streams and Lambda Expressions.
Practise 1Z0-829 questions linked to Java Platform Overview and Packaging.
Practise 1Z0-829 questions linked to Java I/O API and Securing Applications.
Practise 1Z0-829 questions linked to 1Z0-829 fundamentals.
Practise 1Z0-829 questions linked to 1Z0-829 scenario.
Practise 1Z0-829 questions linked to 1Z0-829 troubleshooting.
Practice this exam
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
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 `List.of()` method returns an immutable list, meaning its elements cannot be added, removed, or replaced. Calling `set()` on an immutable list throws an `UnsupportedOperationException` at runtime, which is why option B is correct.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jun 25, 2026
This 1Z0-829 practice question is part of Courseiva's free Oracle certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 1Z0-829 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.