1Z0-829 Working with Streams and Lambda Expressions Practice Question
Which two statements are true about the peek method of the Stream API? (Choose two.)
⚠ Common exam trap
Test-takers frequently confuse `peek` with `map`, thinking `peek` can modify or transform elements, when in fact `peek` only observes and returns the same elements unchanged.
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.
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.
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.
- ✓
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.
- ✗
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.
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