import static org.assertj.core.api.Assertions.assertThat;

public class LerneReduce {
    public static void main(String[] args) {
        List<String> bros = TestDataProvider.getBrothersInArms();

        assertThat(
            bros.stream().reduce((a, b) -> a + ", " + b).get()
        ).isEqualTo("Walther, Hans, Erich, Paul");

        IntStream oneTo3 = IntStream.iterate(1, i -> ++i).limit(3);
        assertThat(
             oneTo3.reduce((i1, i2) -> i1 + i2).getAsInt()
        ).isEqualTo(6);

    }
}