Working with Arrays and Collections →hardMultiple ChoiceObjective-mapped

1Z0-829 Working with Arrays and Collections Practice Question

Exhibit

Refer to the exhibit.
```
List<String> list = new ArrayList<>(List.of("A", "B", "C"));
for (String s : list) {
    if (s.equals("B")) {
        list.remove(s);
    }
}
System.out.println(list);
```

What is the result of executing the code in the exhibit?

⚠ Common exam trap

Candidates often think removing an element during iteration is safe if done via the list's remove() method, not realizing that the for-each loop's iterator detects the structural modification and throws ConcurrentModificationException.

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

ConcurrentModificationException is thrown.

The code uses an ArrayList and iterates over it with an enhanced for-each loop while simultaneously removing an element via the list's remove() method. This structural modification directly from the list (not via the iterator's remove()) triggers a ConcurrentModificationException because the iterator's modCount check fails. The exception is thrown at the next iteration attempt after the removal.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✗
The code compiles and runs without output.
Why it's wrong here
Exception is thrown and printed.
✗
[A, C]
Why it's wrong here
Would be result if no exception, but exception is thrown.
✓
ConcurrentModificationException is thrown.
Why this is correct
Modification during enhanced for loop causes exception.
✗
[A, B]
Why it's wrong here
Incorrect removal.

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1Z0-829 Working with Arrays and Collections Practice Question

Exhibit

Why each option matters

Option-by-option breakdown

Related to this question