flatMap() 함수

flatMap() 함수 

:map 함수는 1대1 함수라면 flatMap함수는 일대다 혹은 일대일 Observable 함수이다. 

public class FlatMap {


    public static void main(String[] args) {

        String[] ball = {"1", "2", "3", "4", "5"};
        Observable<String> source = Observable.fromArray(ball)
                .flatMap(getDoubleDiamond);
        source.subscribe(System.out::println);

    }

    static  Function<String, Observable<String>> getDoubleDiamond = ball -> Observable.just(ball + "<>", ball + "<>");

}

public class Ex4 {

    public static void main(String[] args) {

        Scanner in = new Scanner(System.in);
        System.out.println("GuGuDan Input :" );

        int dan = Integer.parseInt(in.nextLine());

          for (int row = 1; row <= 9; row++) {
            System.out.println( dan + " *  " + row + " = " + dan * row);
        }

        System.out.println("===========================");

        // change for to Observable
        Observable<Integer> source = Observable.range(1, 9);
        source.subscribe(row -> System.out.println( dan + " *  " + row + " = " + dan * row));


        System.out.println("===========================");

        Function<Integer, Observable<String>> gugudan = num ->
                Observable.range(1, 9).map(row -> num + " * " + row + " = " + dan * row);

        Observable<String> source2 = Observable.just(dan).flatMap(gugudan);
        source2.subscribe(System.out::println);


        System.out.println("===========================");

        Observable<String> source3 = Observable.just(dan)
                .flatMap( num -> Observable.range(1, 9)
                                            .map(row -> num + " * " + row + " = " + dan * row)
                );

        source3.subscribe(System.out::println);

    }
}