The answer is to use an explicit Iterator and call its remove() method, as this is the only safe removal during iteration that guarantees correct behavior without throwing a ConcurrentModificationException. The Iterator.remove() method works by modifying the underlying collection in a way that keeps the iterator’s internal state consistent, avoiding the structural modification detection that triggers the exception. On the Oracle Certified Professional Java SE 17 Developer 1Z0-829 exam, this question tests your understanding of fail-fast iterators and the proper use of the Iterator pattern, often appearing as a trap where candidates mistakenly use List.remove() inside a for-each loop. A common memory tip is to remember that the Iterator is the only object that can safely remove elements while iterating—think of it as the “authorized remover” that keeps the collection’s modification count in sync.
1Z0-829 Controlling Program Flow Practice Question
This 1Z0-829 practice question tests your understanding of controlling program flow. 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.
A developer needs to iterate over a List<String> and remove elements that are null. Which approach guarantees correct behavior without throwing a ConcurrentModificationException?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use an Iterator explicitly and call its remove() method
Option A is correct because Iterator.remove() is the safe way to modify a collection during iteration. Option B is wrong because using List.remove() inside a for-each loop will cause ConcurrentModificationException. Option C is wrong because while it may work, it is not the recommended best practice and can be error-prone. Option D is wrong because using a for loop with index decrement also works but is not the idiomatic Java approach.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Use a for-each loop and call list.remove() on the current element
Why it's wrong here
Modifying the list during for-each iteration throws ConcurrentModificationException.
✗
Use a Stream's filter() method and collect the results
Why it's wrong here
Filtering creates a new list, which is acceptable but not the only way; it doesn't modify the original list in place.
✗
Use a traditional for loop with an index that decrements
Why it's wrong here
While this avoids the exception, it is not the standard Java best practice for this scenario.
✓
Use an Iterator explicitly and call its remove() method
Why this is correct
Iterator.remove() is the safe way to remove elements during iteration.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Trap categories for this question
Scenario analysis trap
While this avoids the exception, it is not the standard Java best practice for this scenario.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
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
Got this wrong? Here's your next step.
Identify which 1Z0-829 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Controlling Program Flow — This question tests Controlling Program Flow — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use an Iterator explicitly and call its remove() method — Option A is correct because Iterator.remove() is the safe way to modify a collection during iteration. Option B is wrong because using List.remove() inside a for-each loop will cause ConcurrentModificationException. Option C is wrong because while it may work, it is not the recommended best practice and can be error-prone. Option D is wrong because using a for loop with index decrement also works but is not the idiomatic Java approach.
What should I do if I get this 1Z0-829 question wrong?
Identify which 1Z0-829 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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