问题
How is IntStream, DoubleStream, or LongStream better than regular stream in Java 8?
Do these threads have high performance or maybe usability?
回答1:
Stream<Integer> etc. have to work with boxed values (Integer instead of primitive int) which takes significantly more memory and usually a lot of boxing/unboxing operations (depending on your code). Why only Int/Double/Long? Just because they were expected to be used most often.
Same applies to OptionalInt and friends and all the functional interfaces.
For collections (lists/maps/sets) there are many third-party libraries providing primitive specialization for the same reason. Really the problem there is even more acute because with streams you don't (usually; sorted() is a counter-example) need to store many values in memory.
来源：https://stackoverflow.com/questions/54840920/what-is-the-advantage-of-intstream-over-usual-stream