Compares the difference between map and flatMap in Java 8

java-map-vs-flatMap.java

import java.util.function.Function;
import java.util.stream.Stream;

public class Foo {
    void test() {
        Function<Integer, Stream<Integer>> transformer = it -> Stream.of(it * 10, it * 100, it * 1000);

        Stream<Integer> myInts = Stream.of(1, 2, 3);

        // contains [ [10, 100, 1000], [20, 200, 2000], [30, 300, 3000] ]
        Stream<Stream<Integer>> nestedInts = myInts.map(transformer);

        // contains [ 10, 100, 1000, 20, 200, 2000, 30, 300, 3000 ]
        Stream<Integer> flatInts = myInts.flatMap(transformer);
    }
}