检查流中的 instanceof [英] Check instanceof in stream
本文介绍了检查流中的 instanceof的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
I have the following expression:
scheduleIntervalContainers.stream()
.filter(sic -> ((ScheduleIntervalContainer) sic).getStartTime() != ((ScheduleIntervalContainer)sic).getEndTime())
.collect(Collectors.toList());
...where scheduleIntervalContainers
has element type ScheduleContainer
:
final List<ScheduleContainer> scheduleIntervalContainers
Is it possible to check the type before the filter?
解决方案
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());
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