问题描述
我有列表< Users>
。我想用特定的用户名获取流中(第一个)用户的索引。我不想实际要求用户
为 .equals()
描述用户
,只是为了拥有相同的用户名。
I have a List<Users>
. I want to get the index of the (first) user in the stream with a particular username. I don't want to actually require the User
to be .equals()
to some described User
, just to have the same username.
我可以想到这样做的丑陋方法(迭代和计数),但感觉应该有一个很好的方法来做到这一点,可能是通过使用Streams。到目前为止,我所拥有的最好的是:
I can think of ugly ways to do this (iterate and count), but it feels like there should be a nice way to do this, probably by using Streams. So far the best I have is:
int index = users.stream()
.map(user -> user.getName())
.collect(Collectors.toList())
.indexOf(username);
这不是我写过的最糟糕的代码,但它并不好。它也不是那么灵活,因为它依赖于一个带有 .equals()
函数的类型的映射函数来描述你正在寻找的属性;我宁愿有一些可以用于任意功能< T,布尔>
Which isn't the worst code I've ever written, but it's not great. It's also not that flexible, as it relies on there being a mapping function to a type with a .equals()
function that describes the property you're looking for; I'd much rather have something that could work for arbitrary Function<T, Boolean>
任何人都知道怎么做?
Anyone know how?
推荐答案
偶尔在java中没有pythonic zipWithIndex
。所以我遇到了类似的东西:
Occasionally there is no pythonic zipWithIndex
in java. So I came across something like that:
OptionalInt indexOpt = IntStream.range(0, users.size())
.filter(i -> searchName.equals(users.get(i)))
.findFirst();
或者你可以从 zipWithIndex href =https://github.com/poetix/protonpack =noreferrer> protonpack 库
Alternatively you can use zipWithIndex
from protonpack library
注意
如果users.get不是常量时间操作,那么该解决方案可能会非常耗时。
这篇关于Stream Way获取匹配boolean的第一个元素的索引的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!