RxJava flatMap single

gistfile1.java

/**
 * Do 1 heavy operation, when successful, fire 2 more heavy operations sequentially that use the first operation's data
 */
private List<String> getHeavyList() {
    List<String> list = new ArrayList<>();

    list.add("First string");
    list.add("Second string");
    list.add("Third string");

    return list;
}

private int getIntFromList(List<String> strings) {
    return 1;
}

private boolean getBoolFromList(List<String> strings) {
    return true;
}

Single<List<String>> heavyOperationObservable = Single.fromCallable(new Callable<List<String>>() {
    @Override
    public List<String> call() {
        return getHeavyList();
    }
}).subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread());

heavyOperationObservable.subscribeWith(new DisposableSingleObserver<List<String>>() {
    @Override
    public void onSuccess(final List<String> strings) {
        final Single<Integer> singleInt = Single.fromCallable(new Callable<Integer>() {
            @Override
            public Integer call() {
                return getIntFromList(strings);
            }
        }).subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread());

        final Single<Boolean> singleBoolean = Single.fromCallable(new Callable<Boolean>() {
            @Override
            public Boolean call() throws Exception {
                return getBoolFromList(strings);
            }
        }).subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread());

        singleInt.flatMap(new Function<Integer, Single<Boolean>>() {
            @Override
            public Single<Boolean> apply(@io.reactivex.annotations.NonNull Integer integer) throws Exception {
                return singleBoolean;
            }
        }).subscribeWith(new DisposableSingleObserver<Boolean>() {
            @Override
            public void onSuccess(Boolean aBoolean) {
                Log.i("RxJava", "boolean: " + aBoolean);
            }

            @Override
            public void onError(Throwable e) {

            }
        });
    }

    @Override
    public void onError(Throwable e) {

    }
});