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.
What is the result of the following code? List<String> list = List.of("A", "B"); list.add("C"); System.out.println(list);
[A, B, C]
Why wrong: List.of returns immutable list, add not allowed.
[A, B]
Why wrong: Exception is thrown, not printed.
An exception is thrown at runtime
UnsupportedOperationException thrown.
Compilation error
Why wrong: list.add is a valid method call, compiles.
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 exception is thrown at runtime
The `List.of()` factory method returns an immutable list. Calling `add()` on an immutable list throws an `UnsupportedOperationException` at runtime, so the code does not compile or run successfully. Option C is correct because the exception is thrown when the `add` method is invoked.
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.
[A, B, C]
Why it's wrong here
List.of returns immutable list, add not allowed.
[A, B]
Why it's wrong here
Exception is thrown, not printed.
An exception is thrown at runtime
Why this is correct
UnsupportedOperationException thrown.
Related concept
Read the scenario before looking for a memorised answer.
Compilation error
Why it's wrong here
list.add is a valid method call, compiles.
Common exam traps
The trap here is that candidates often assume `List.of()` returns a regular mutable `ArrayList` or that the code will simply ignore the `add` call, but the exam tests the specific runtime exception behavior of immutable collections created by factory methods.
Detailed technical explanation
Under the hood, `List.of()` returns an instance of an internal immutable list class (e.g., `ImmutableCollections.List12` or `ListN`) that overrides mutating methods like `add`, `remove`, and `set` to throw `UnsupportedOperationException`. This design enforces immutability for safety in concurrent or functional programming contexts. A real-world scenario is using `List.of()` to define a fixed set of configuration keys that should never be altered accidentally.
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 exception is thrown at runtime — The `List.of()` factory method returns an immutable list. Calling `add()` on an immutable list throws an `UnsupportedOperationException` at runtime, so the code does not compile or run successfully. Option C is correct because the exception is thrown when the `add` method is invoked.
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
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.
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