使用lambda或Stream API合并流以产生交替序列 [英] merge streams to produce alternating sequence using lambda or Stream API

问题描述

我有一些代码可以按预期返回Stream，但是也许可以用某种类型的lambda或stream()操作代替它，而不用在while循环中耗尽迭代器?

I have some code which returns a Stream as intended, but maybe it can be replaced with some type of lambda or stream() operation instead of exhausting the iterators in a while loop?

这只是一种方法，它交替使用流first和second中的元素，并在其中一个元素用完时停止.

It is just a method that alternates elements from the streams first and second and stops when one of them runs out of elements.

public static <T>Stream<T> alternatingSequence(Stream<T> first, Stream<T> second){
        Iterator<T> iteratorFirst = first.iterator();
        Iterator<T> iteratorSecond = second.iterator();
        Stream<T> resultStream = Stream.empty();
        while (iteratorFirst.hasNext() && iteratorSecond.hasNext()){
            resultStream = Stream.concat(resultStream, Stream.of(iteratorFirst.next(), iteratorSecond.next()));
        }
        return resultStream;
    }
}

推荐答案

使用

Using Guava's Streams.zip you can combine the two streams into a stream of two-element streams, which you may then simply flatten to produce an alternating sequence:

return Streams.zip(first, second, (arg1, arg2) -> Stream.of(arg1, arg2))
    .flatMap(Function.identity());

一个警告是，生成的流无法有效拆分(请参阅链接的文档).这可能会损害并行性能.

One caveat is that the resulting stream is not efficiently splittable (see linked doc). This may harm parallel performance.

注意:

如果您无权访问番石榴，则可以实现自己的zip(a, b, bifunc)，如此处所示.

If you don't have access to Guava then you can implement your own zip(a, b, bifunc) as shown here.

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