Check instanceof in stream

You can apply another filter in order to keep only the ScheduleIntervalContainer instances, and adding a map will save you the later casts :

scheduleIntervalContainers.stream()    .filter(sc -> sc instanceof ScheduleIntervalContainer)    .map (sc -> (ScheduleIntervalContainer) sc)    .filter(sic -> sic.getStartTime() != sic.getEndTime())    .collect(Collectors.toList());

Or, as Holger commented, you can replace the lambda expressions with method references if you prefer that style:

scheduleIntervalContainers.stream()    .filter(ScheduleIntervalContainer.class::isInstance)    .map (ScheduleIntervalContainer.class::cast)    .filter(sic -> sic.getStartTime() != sic.getEndTime())    .collect(Collectors.toList());

A pretty elegant option is to use method reference of class:

scheduleIntervalContainers  .stream()  .filter( ScheduleIntervalContainer.class::isInstance )  .map( ScheduleIntervalContainer.class::cast )  .filter( sic -> sic.getStartTime() != sic.getEndTime())  .collect(Collectors.toList() );

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 <T, R> Function<T, Stream<R>> select(Class<R> 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