FileSystemTest.java

public class FileSystemTest {
    @Test
    public void t1() throws Exception {
        long startModified = f.lastModified();

        Observable.interval(5, TimeUnit.SECONDS)
                .map(i -> {
                    System.out.println("map ");
                    long l = f.lastModified();
                    if (l % 3 == 0) {
                        throw new RuntimeException();
                    }
                    return l;
                })
                .scan(startModified, (l, n) -> {
                    System.out.println(l+":"+n);
                    if (!l.equals(n)) {
                        System.out.println("Change!!");
                        return n;
                    }
                    return l;
                })
                .retry((i, e) -> {
                    System.out.println(e + ", total error: " + i);
                    return true;
                })
                .subscribe();

        Thread.sleep(100000);
   }
}