JuniorTheoryCommon

What does the program print?

JAVA

import java.util.List;

public class Main {
    public static void main(String[] args) {
        List<Integer> xs = List.of(1, 2, 3);
        xs.stream().map(x -> {
            System.out.print(x + " ");
            return x * 2;
        });
        System.out.println("end");
    }
}

end

Expecting 1 2 3 end: map only adds a step to the pipeline; its lambda runs once a terminal operation such as toList starts it, and here there is none.
Expecting the stream to run later on its own: laziness means the work waits for a terminal operation, and without one it never happens.

What does the program print if .toList() is added after map?
In what order do filter and map see the elements once a terminal operation runs?

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JuniorTheoryCommon

What does the program print?

JAVA

import java.util.List;

public class Main {
    public static void main(String[] args) {
        List<Integer> xs = List.of(1, 2, 3);
        xs.stream().map(x -> {
            System.out.print(x + " ");
            return x * 2;
        });
        System.out.println("end");
    }
}

end

Expecting 1 2 3 end: map only adds a step to the pipeline; its lambda runs once a terminal operation such as toList starts it, and here there is none.
Expecting the stream to run later on its own: laziness means the work waits for a terminal operation, and without one it never happens.

What does the program print if .toList() is added after map?
In what order do filter and map see the elements once a terminal operation runs?

Back to questions Open topic in roadmap →Answer it yourself — Quiz