The answer is `transactions.stream().filter(t -> t.getAmount() > 100).collect(Collectors.toList())`, as this best practice combines declarative filtering with efficient collection. The Stream API’s `filter` method applies lazy evaluation, meaning intermediate operations are not executed until a terminal operation like `collect` is invoked, which optimizes performance by processing elements only once. For the Oracle Certified Professional Java SE 17 Developer 1Z0-829 exam, this question tests your understanding of functional-style data processing and the distinction between intermediate and terminal operations. A common trap is using `forEach` with an external list or a parallel stream unnecessarily, which sacrifices readability or introduces concurrency overhead. Remember the memory tip: “Filter first, collect last — lazy streams make the pipeline fast.” This pattern is the standard for filtering a list with Stream API because it clearly separates the filtering logic from the result gathering, aligning with Java’s move toward immutable, side-effect-free code.
1Z0-829 Working with Arrays and Collections Practice Question
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.
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?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Option A is correct because 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.
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.
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may 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.
Detailed technical explanation
How to think about this question
Under the hood, `Stream.filter` creates a stateless intermediate operation that lazily evaluates the predicate, and `collect(Collectors.toList())` uses a mutable reduction with a `Supplier` (e.g., `ArrayList::new`), an accumulator, and a combiner for thread-safe parallel processing. In real-world scenarios, using `Collectors.toList()` guarantees a new mutable list, while `toList()` (Java 16+) returns an unmodifiable list, which could be a subtle trap if immutability is not desired.
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.
TExam Day Tips
→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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Working with Arrays and Collections — This question tests Working with Arrays and Collections — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: transactions.stream().filter(t -> t.getAmount() > 100).collect(Collectors.toList()) — Option A is correct because 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.
What should I do if I get this 1Z0-829 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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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