Check instanceof in stream

Question

I have the following expression:

scheduleIntervalContainers.stream()
        .filter(sic -> ((ScheduleIntervalContainer) sic).getStartTime() != ((ScheduleInte         


        

Answer 1

There is a small problem with @Eran solution - typing class name in both filter and map is error-prone - it is easy to forget to change the name of the class in both places. An improved solution would be something like this:

private static  Function> select(Class clazz) {
    return e -> clazz.isInstance(e) ? Stream.of(clazz.cast(e)) : null;
}

scheduleIntervalContainers
  .stream()
  .flatMap(select(ScheduleIntervalContainer.class))
  .filter( sic -> sic.getStartTime() != sic.getEndTime())
  .collect(Collectors.toList());   

However there might be a performance penalty in creating a Stream for every matching element. Be careful to use it on huge data sets. I've learned this solution from @Tagir Vailev