1Z0-829 Working with Streams and Lambda Expressions Practice Question
This 1Z0-829 practice question tests your understanding of working with streams and lambda expressions. 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 company needs to process a stream of orders and filter out orders that are not in the 'SHIPPED' status. Then they want to collect the order IDs into a list. Which of the following correctly uses lambda expressions to achieve this?
Option D is correct because it first filters the stream to include only orders with status 'SHIPPED' using a lambda expression that calls equals() on the status string, then maps each order to its ID using a method reference, and finally collects the IDs into a list. This correctly uses lambda expressions and the Stream API to achieve the requirement.
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.
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Oracle often tests the distinction between using equals() vs == for string comparison in lambda expressions, and the correct order of stream operations (filter before map) to avoid type mismatches or logical errors.
Detailed technical explanation
How to think about this question
The Stream API's filter() method expects a Predicate functional interface, which returns a boolean. Using equals() for string comparison is crucial because == or != checks reference equality, not logical equality, which can lead to bugs with string interning. The map() operation transforms each element, and Collectors.toList() accumulates results into a mutable List. In real-world scenarios, order statuses are often stored as strings, and using equals() ensures correct filtering regardless of string object identity.
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 Streams and Lambda Expressions — This question tests Working with Streams and Lambda Expressions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: orders.stream().filter(o -> o.getStatus().equals("SHIPPED")).map(Order::getId).collect(Collectors.toList()) — Option D is correct because it first filters the stream to include only orders with status 'SHIPPED' using a lambda expression that calls equals() on the status string, then maps each order to its ID using a method reference, and finally collects the IDs into a list. This correctly uses lambda expressions and the Stream API to achieve the requirement.
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.
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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