想问一个各位大牛技术问题，这个操作用 java8 分组怎么做？

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有一个对象集合 Stream stream = Stream.of(new People("张三","老师"),new People("李四","学生"),new People("王五","校长"));

想通过分组得类似于这样的分组 Map<Boolean,List<People>> ;

当为 true 时，List 集合为｛"张三","李四","王五")

当为 false 时候，list 集合为｛"张三老师"，"李四学生","王五校长"｝；

5 replies • 2020-09-30 09:46:14 +08:00

lululau

Sep 23, 2020

问题描述得一堆错误，尝试理解下你的意图：

var people = List.of(new Person("张三","老师"),new Person("李四","学生"),new Person("王五","校长"));
var result = Map.of(true, people.stream().map(Person::getName).collect(Collectors.toList()),
false, people.stream().map(Person::getNameWithRole).collect(Collectors.toList()));

lululau

Sep 23, 2020

另外一个思路：

var result = people.stream().flatMap(p -> Steam.of(Pair.of(true, p.getName()), Pair.of(false, p.getNameWithRole()))).collect(Collectors.groupingBy(Pair::getLeft, Collectors.mapping(Pair.getRight), Collectors.toList()))

lululau

Sep 23, 2020

更正：

var result = people.stream().flatMap(p -> Steam.of(Pair.of(true, p.getName()), Pair.of(false, p.getNameWithRole()))).collect(Collectors.groupingBy(Pair::getLeft, Collectors.mapping(Pair::getRight, Collectors.toList()))

thatiam92

Sep 28, 2020

3q :) 问题虽然描述得不好 <-.->，但根据思路找到了解决办法

siweipancc

Sep 30, 2020

peoples.stream().collect(LinkedMultiValueMap::new, (m, p) -> { m.add(true, p.getName());m.add(false, p.getName().concat(p.getPosition())); }, Map::putAll);

为什么会有这种奇葩的玩法 OTZ，不都是映射域值吗。