Working with Arrays and Collections →mediumMultiple ChoiceObjective-mapped

1Z0-829 Working with Arrays and Collections Practice Question

A developer needs to filter a list of transactions where the amount is greater than 100 and collect the results into a new list. Which approach is best practice for readability and performance?

⚠ Common exam trap

Candidates often choose Option D, thinking `removeIf` is a filter, but it mutates the original collection and does not create a new list, which is explicitly required by the question.

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

✓

transactions.stream().filter(t -> t.getAmount() > 100).collect(Collectors.toList())

It uses the Stream API's `filter` method to declaratively select transactions with an amount greater than 100, and `collect(Collectors.toList())` to gather results into a new list. This approach is both readable and performant, leveraging lazy evaluation and internal iteration for efficient processing.

Answer analysis

Option-by-option breakdown

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

✓
transactions.stream().filter(t -> t.getAmount() > 100).collect(Collectors.toList())
Why this is correct
Stream API is best practice for filtering and collecting into a new list.
✗
List<Transaction> result = new ArrayList<>(); for(Transaction t : transactions) { if(t.getAmount() > 100) result.add(t); }
Why it's wrong here
Using a for loop is more verbose and less declarative than streams.
✗
transactions.stream().filter(t -> t.getAmount() > 100).toArray()
Why it's wrong here
Collecting to an array is less flexible than a list for further operations.
✗
transactions.removeIf(t -> t.getAmount() <= 100)
Why it's wrong here
This modifies the original list, which may not be intended.

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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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