Observable.range()

To emit a consecutive range of integers, you can use Observable.range(). This will emit each number from a start value and increment each emission until the specified count is reached. These numbers are all passed through the onNext() event, followed by the  onComplete() event:

    import io.reactivex.Observable;

    public class Launcher {
      public static void main(String[] args) {
        Observable.range(1,10)
          .subscribe(s -> System.out.println("RECEIVED: " + s));

      }
   }

The output is as follows:

    RECEIVED: 1
    RECEIVED: 2
    RECEIVED: 3
    RECEIVED: 4
    RECEIVED: 5
    RECEIVED: 6
    RECEIVED: 7
    RECEIVED: 8
    RECEIVED: 9
    RECEIVED: 10

Note closely that the two arguments for Observable.range() are not lower/upper bounds. The first argument is the starting value. The second argument is the total count of emissions, which will include both the initial value and incremented values. Try emitting Observable.range(5,10), and you will notice that it emits 5 followed by the next nine consecutive integers following it (for a grand total of 10 emissions):

    import io.reactivex.Observable;

    public class Launcher {
      public static void main(String[] args) {
        Observable.range(5,10)
        .subscribe(s -> System.out.println("RECEIVED: " + s));

      }
     }

The output is as follows:

    RECEIVED: 5
    RECEIVED: 6
    RECEIVED: 7
    RECEIVED: 8
    RECEIVED: 9
    RECEIVED: 10
    RECEIVED: 11
    RECEIVED: 12
    RECEIVED: 13
    RECEIVED: 14