Working with Streams and Lambda Expressions →mediumMultiple ChoiceObjective-mapped

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

Exhibit

Refer to the exhibit.
List<String> list = List.of("a", "b", "c");
Stream<String> stream = list.stream();
stream.filter(s -> s.startsWith("b")).forEach(System.out::print);
stream.forEach(System.out::print);

What is the result of executing this code?

⚠ Common exam trap

The trap here is that candidates often forget that streams are single-use and incorrectly assume that chaining multiple terminal operations on the same stream is allowed, leading them to pick a concatenated output like 'baaabc' instead of recognizing the runtime exception.

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

✓

An exception is thrown at runtime.

The code attempts to call `findFirst()` on a `Stream<String>` that has already been consumed by a previous terminal operation (`forEach`). In Java, streams are single-use; after a terminal operation is executed, the stream is closed and cannot be reused. Any attempt to perform another terminal operation on the same stream throws an `IllegalStateException` at runtime.

Answer analysis

Option-by-option breakdown

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

✓
An exception is thrown at runtime.
Why this is correct
IllegalStateException is thrown when a terminal operation is called on an already-consumed stream.
✗
bbc
Why it's wrong here
Incorrect output.
✗
Compilation error
Why it's wrong here
The code compiles; the error occurs at runtime.
✗
baaabc
Why it's wrong here
This would happen if the stream could be used twice, but it cannot.

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

Exhibit

Why each option matters

Option-by-option breakdown

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