Working with Arrays and Collections →easyMultiple ChoiceObjective-mapped

1Z0-829 Working with Arrays and Collections Practice Question

Given ArrayList<Integer> numbers = new ArrayList<>(List.of(1,2,3,4)); Which statement will insert element 10 at index 2?

⚠ Common exam trap

Many exam-takers confuse the `add(index, element)` method with `set(index, element)`, mistakenly thinking both insert, or they reverse the argument order, expecting `add(element, index)` as in some other languages.

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

✓

numbers.add(2,10);

The `ArrayList.add(int index, E element)` method inserts the specified element at the given index, shifting existing elements to the right. Here, `numbers.add(2,10)` inserts 10 at index 2, resulting in the list [1,2,10,3,4].

Answer analysis

Option-by-option breakdown

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

✗
numbers.add(10,2);
Why it's wrong here
The add method expects index first, then element; this would attempt to add at index 10, causing IndexOutOfBoundsException.
✓
numbers.add(2,10);
Why this is correct
Inserts 10 at index 2, shifting subsequent elements to the right.
✗
numbers.set(2,10);
Why it's wrong here
set replaces the element at index 2, not insert.
✗
numbers.insert(2,10);
Why it's wrong here
No insert method exists in List or ArrayList.

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1Z0-829 Working with Arrays and Collections Practice Question

Why each option matters

Option-by-option breakdown

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