java - 是否可以将流收集到两个收集器中

Question

我有一个字符串列表，我想在其中写入不同的字符串集到一个文件中，并将其转换为 UUID 并将其存储在另一个变量中。Java 8 lambda 是否可行？如何实现？

我要求两个收集器的原因是为了避免运行它进入第二个循环。

Answer 1

这在 Java 12 中是可能的其中引入了 Collectors.teeing:

public static <T, R1, R2, R>
Collector<T, ?, R> teeing(Collector<? super T, ?, R1> downstream1,
                          Collector<? super T, ?, R2> downstream2,
                          BiFunction<? super R1, ? super R2, R> merger);

Returns a Collector that is a composite of two downstream collectors. Every element passed to the resulting collector is processed by both downstream collectors, then their results are merged using the specified merge function into the final result.

例子:

Entry<Long, Long> entry = Stream
        .of(1, 2, 3, 4, 5)
        .collect(teeing(
                filtering(i -> i % 2 != 0, counting()),
                counting(),
                Map::entry));

System.out.println("Odd count: " + entry.getKey());
System.out.println("Total count: " + entry.getValue());