Exercise – Creating io.reactivex.Observable

Write code that demonstrates several ways to create io.reactivex.Observable. In each example, subscribe to the created Observable object and print the emitted values.

Note

We did not discuss this so you will need to study the RxJava2 API and look up examples on the internet.

Answer

Here are six of the methods that allow you to create io.reactivex.Observable:

//1
Observable.just("Hi!").subscribe(System.out::println); //prints: Hi!
//2
Observable.fromIterable(List.of("1","2","3"))
          .subscribe(System.out::print); //prints: 123
System.out.println();
//3
String[] arr = {"1","2","3"};
Observable.fromArray(arr).subscribe(System.out::print); //prints: 123
System.out.println();
//4
Observable.fromCallable(()->123)
          .subscribe(System.out::println); //prints: 123
//5
ExecutorService pool = Executors.newSingleThreadExecutor();
Future<String> future = pool
        .submit(() -> {
            Thread.sleep(100);
            return "Hi...