Java流可将字符串拆分并收集到Map [英] Java streams to split and collect string to a Map

问题描述

我有一个像这样的字符串

I have a string like this

String input = "abc|label1 cde|label2 xyz|label1 mno|label3 pqr|label2";

我想创建一个看起来像(过滤掉label3之后)的地图label1-> {abc，xyz}label2-> {cde，pqr}label3-> {mno}

I want to create a Map which looks like (after filtering out label3} label1 -> {abc,xyz} label2 -> {cde,pqr} label3 -> {mno}

这是我到目前为止可以做的

This is what I could do so far

  Map<String, List<String>> result = Arrays.stream(inputString.split(" "))
                .filter(i -> !i.contains("label3"))
                .map(i -> i.split("//|"))

还有第二个用例:我如何只将令牌收集在一个字符串中

Also second use case: how do I just collect the tokens all in one string

abc | label1 cde | label2 xyz | label1 mno | label3 pqr | label2 =>"abc cde xyzmno pqr"

abc|label1 cde|label2 xyz|label1 mno|label3 pqr|label2 => "abc cde xyz mno pqr"

推荐答案

首先用空格分隔 作为分隔符

First split the with space as delimiter

input.split(" ") //[abc|label1, cde|label2, xyz|label1, mno|label3, pqr|label2]

然后使用管道 \ 作为分隔符分割数组中的每个字符串，并使用 Collectors.groupingBy

And then split each string in array with pipe \ as delimiter and use Collectors.groupingBy

Map<String, List<String>> map = Arrays.stream(input.split(" "))
                                      .map(s -> s.split("\\|"))
                                      .collect(Collectors.groupingBy(str -> str[1], 
                                             Collectors.mapping(str -> str[0], Collectors.toList())));

输出:

{label1=[abc, xyz], label2=[cde, pqr], label3=[mno]}

使用 Collectors.joining 将值从 Map 收集到String

Use Collectors.joining to collect value from Map into String

String result = map.values()
                   .stream()
                   .flatMap(Collection::stream)
                   .collect(Collectors.joining(" "));

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