在使用流迭代列表时获取索引 [英] Get Index while iterating list with stream

问题描述

List<Rate> rateList = 
       guestList.stream()
                .map(guest -> buildRate(ageRate, guestRate, guest))
                .collect(Collectors.toList());  

class Rate {
    protected int index;
    protected AgeRate ageRate;
    protected GuestRate guestRate;
    protected int age;
}

在上面的代码中，可以在buildRate方法内传递guestList的索引.我在构建Rate时也需要传递索引，但是无法通过Stream获取索引.

In the above code, is it possible to pass index of guestList inside buildRate method. I need to pass index also while building Rate but could not manage to get index with Stream.

推荐答案

您尚未提供buildRate的签名，但是我假设您希望首先传递guestList元素的索引. (在ageRate之前).您可以使用IntStream获取索引，而不必直接处理元素:

You haven't provided the signature of buildRate, but I'm assuming you want the index of the elements of guestList to be passed in first (before ageRate). You can use an IntStream to get indices rather than having to deal with the elements directly:

List<Rate> rateList = IntStream.range(0, guestList.size())
    .mapToObj(index -> buildRate(index, ageRate, guestRate, guestList.get(index)))
    .collect(Collectors.toList());

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