Working with Streams and Lambda Expressions →easyMultiple ChoiceObjective-mapped

1Z0-829 Working with Streams and Lambda Expressions Practice Question

Exhibit

List<String> list = Arrays.asList("a", "b", "c");
Stream<String> stream = list.stream();
stream.forEach(System.out::print);
stream.forEach(System.out::print);

Refer to the exhibit. What is the result?

⚠ Common exam trap

Oracle Java 17 exams often test the misconception that a stream can be reused like a collection, leading candidates to expect multiple traversals or to overlook the single-use contract enforced by the Stream API.

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

✓

IllegalStateException

The code attempts to call `findAny()` on a `Stream` that has already been consumed by a terminal operation (`forEach`). Once a terminal operation is executed on a stream, the stream is closed and cannot be reused. Any subsequent call to a terminal operation on the same stream reference throws `IllegalStateException`. Option C is correct because the second terminal operation violates the single-use contract of streams.

Answer analysis

Option-by-option breakdown

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

✗
abc
Why it's wrong here
Only the first forEach prints abc, but the second forEach will cause an exception.
✗
NullPointerException
Why it's wrong here
No null pointer issue here.
✓
IllegalStateException
Why this is correct
Correct. A stream cannot be reused after a terminal operation.
✗
abcabc
Why it's wrong here
The stream is already consumed; the second forEach will not execute.

Go deeper

1Z0-829 Working with Streams and Lambda Expressions Practice Question

Exhibit

Why each option matters

Option-by-option breakdown

Related to this question