Working with Streams and Lambda Expressions →mediumMultiple ChoiceObjective-mapped

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

Exhibit

List<Integer> numbers = List.of(1, 2, 3, 4, 5);
int sum = numbers.stream()
                 .reduce(0, (a, b) -> a + b);
System.out.println(sum);

Refer to the exhibit. What is the output?

```java

import java.util.stream.IntStream;

public class Example {
    public static void main(String[] args) {
        int sum = IntStream.rangeClosed(0, 5)

.filter(i -> i >= 0) .sum(); System.out.println(sum);

}
}

```

⚠ Common exam trap

The trap here is that candidates often miscount the number of elements produced by `rangeClosed` versus `range`, leading to off-by-one errors in the sum.

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

✓

The stream pipeline starts with `IntStream.rangeClosed(0, 5)` producing the integers 0, 1, 2, 3, 4, 5. The filter passes all these values, and the map is an identity function (or absent). The reduction sums them: 0+1+2+3+4+5 = 15. Therefore, the output is 15.

Answer analysis

Option-by-option breakdown

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

✗
0
Why it's wrong here
Incorrect; identity is used as starting value but final sum is 15.
✓
15
Why this is correct
Correct.
✗
10
Why it's wrong here
Incorrect; sum of 1 to 5 is 15.
✗
5
Why it's wrong here
Incorrect.

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