- A
It is primarily used for debugging purposes.
peek is intended to aid in debugging by allowing observation of elements as they pass through the pipeline.
- B
It is an intermediate operation.
peek returns a stream consisting of the elements of the original stream, performing the provided action on each element.
- C
It can be used to modify the elements of the stream.
Why wrong: peek is designed for debugging; modifying state is discouraged and can lead to undefined behavior.
- D
It is a terminal operation.
Why wrong: peek is not a terminal operation; it must be followed by a terminal operation to produce a result.
- E
It can be used to transform the elements into a new value.
Why wrong: Transformation is the role of map, not peek.
Question 319 of 519
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.
Which two statements are true about the peek method of the Stream API? (Choose two.)
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
✓
It is primarily used for debugging purposes.
Option A is correct because the `peek` method is designed as a debugging aid to observe elements as they flow through a stream pipeline. It performs the provided action on each element without modifying them, making it ideal for logging or printing intermediate states.
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.
- ✓
It is primarily used for debugging purposes.
Why this is correct
peek is intended to aid in debugging by allowing observation of elements as they pass through the pipeline.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
It is an intermediate operation.
Why this is correct
peek returns a stream consisting of the elements of the original stream, performing the provided action on each element.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
It can be used to modify the elements of the stream.
Why it's wrong here
peek is designed for debugging; modifying state is discouraged and can lead to undefined behavior.
- ✗
It is a terminal operation.
Why it's wrong here
peek is not a terminal operation; it must be followed by a terminal operation to produce a result.
- ✗
It can be used to transform the elements into a new value.
Why it's wrong here
Transformation is the role of map, not peek.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse `peek` with `map`, thinking `peek` can modify or transform elements, when in fact `peek` only observes and returns the same elements unchanged.
Detailed technical explanation
How to think about this question
Under the hood, `peek` is a non-interfering intermediate operation that applies a `Consumer` to each element as it passes through the pipeline. A subtle behavior is that `peek` may not execute at all if the stream is not consumed by a terminal operation, and its action should not rely on element order unless the stream has an encounter order. In real-world debugging, `peek` is often used to inspect data before a `filter` or `map` step without altering the pipeline.
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
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FAQ
Questions learners often ask
What does this 1Z0-829 question test?
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: It is primarily used for debugging purposes. — Option A is correct because the `peek` method is designed as a debugging aid to observe elements as they flow through a stream pipeline. It performs the provided action on each element without modifying them, making it ideal for logging or printing intermediate states.
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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Last reviewed: Jul 4, 2026
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