import io.reactivex.Observable;
import java.util.concurrent.TimeUnit;

public class Launcher {
      public static void main(String[] args) {
        Observable<Long> secondIntervals =
          Observable.interval(1, TimeUnit.SECONDS);

        secondIntervals.subscribe(s -> System.out.println(s));

        /* Hold main thread for 5 seconds
        so Observable above has chance to fire */
        sleep(5000);
      }

      public static void sleep(long millis) {
        try {
          Thread.sleep(millis);
        } catch (InterruptedException e) {
          e.printStackTrace();
        }
      }
}