title: Rxjava : i don't know why this program don't print
body: <p>i don't know why this program don't print. I want print String Object whenever 1 seconds. So I use interval. this program normally compile. but result don't print. why? Help. (I'm Korean. So English is immature. sorry)</p>
  
  <pre>
  public class main {
  
      public static void main(String[] args){
  
  
  
          String str1 = "Apple";
  
          String str2 = "Banana";
  
          String str3 = "Boy";
  
  
  
          ObservableSource tim = Observable.interval(3, TimeUnit.SECONDS);
  
          ObservableSource ss = Observable.just(str1,str2,str3);
  
  
  
  
  
          Observable.zip(tim,ss,new BiFunction() {
  
  
  
              @Override
  
              public String apply(Long t1, String t2) throws Exception {
  
                  System.out.println("ddd");
  
                  return t1+t2;
  
              }
  
  
  
  
  
  
  
          })
  
          .subscribe(new DefaultObserver() {
  
  
  
              @Override
  
              public void onNext(String t) {
  
                  System.out.println(t);
  
              }
  
  
  
              @Override
  
              public void onError(Throwable e) {
  
                  System.out.println("Error!!!");}
  
  
  
              @Override
  
              public void onComplete() {
  
                  System.out.println("Complete!!!");
  
              }
  
          });
  
  
  
  
  
      }
  
  }
  </pre>