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.
Refer to the exhibit.
List<String> list = new ArrayList<>();
list.add("A");
list.add("B");
list.add("C");
list.add("A");
System.out.println(list.indexOf("A"));
System.out.println(list.lastIndexOf("A"));What is the output?
Refer to the exhibit.
List<String> list = new ArrayList<>();
list.add("A");
list.add("B");
list.add("C");
list.add("A");
System.out.println(list.indexOf("A"));
System.out.println(list.lastIndexOf("A"));0 2
Why wrong: lastIndexOf is 3, not 2.
0 3
indexOf returns first occurrence index 0; lastIndexOf returns last occurrence index 3.
1 2
Why wrong: Both values are wrong.
1 3
Why wrong: indexOf is 0, not 1.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
0 3
The code uses a `List.of()` to create an immutable list containing the elements 0, 1, 2, and 3. It then calls `list.removeIf(i -> i % 2 == 0)`, which attempts to remove all even numbers from the list. However, `List.of()` returns an unmodifiable list, so calling `removeIf` throws an `UnsupportedOperationException` at runtime. The output is `0 3` because the exception occurs after printing the original list (0 1 2 3) but before any removal, and the catch block prints the exception's message, which is `null` for this exception type, resulting in `0 3`.
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.
0 2
Why it's wrong here
lastIndexOf is 3, not 2.
0 3
Why this is correct
indexOf returns first occurrence index 0; lastIndexOf returns last occurrence index 3.
Related concept
Read the scenario before looking for a memorised answer.
1 2
Why it's wrong here
Both values are wrong.
1 3
Why it's wrong here
indexOf is 0, not 1.
Common exam traps
The trap here is that candidates assume `List.of()` creates a mutable list like `Arrays.asList()` or `new ArrayList<>()`, and overlook that `removeIf` throws an `UnsupportedOperationException` on immutable lists, leading them to pick the result of a successful removal instead of the actual exception output.
Detailed technical explanation
`List.of()` was introduced in Java 9 and returns an immutable list that does not support structural modification methods like `add`, `remove`, or `removeIf`. The `removeIf` method is a default method in the `Collection` interface that uses an iterator to remove elements, but for unmodifiable collections, it throws `UnsupportedOperationException`. The exception's message is `null` because the default constructor of `UnsupportedOperationException` does not set a detail message, so `e.getMessage()` returns `null`, which prints as `null` in the output.
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: 0 3 — The code uses a `List.of()` to create an immutable list containing the elements 0, 1, 2, and 3. It then calls `list.removeIf(i -> i % 2 == 0)`, which attempts to remove all even numbers from the list. However, `List.of()` returns an unmodifiable list, so calling `removeIf` throws an `UnsupportedOperationException` at runtime. The output is `0 3` because the exception occurs after printing the original list (0 1 2 3) but before any removal, and the catch block prints the exception's message, which is `null` for this exception type, resulting in `0 3`.
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 11, 2026
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