我有一张地图列表,用于存储角色和人名。例如:
List<Map<String, String>> listOfData
1) Role: Batsman
Name: Player1
2)Role: Batsman
Name: Player2
3)Role: Bowler
Name: Player3
角色和名称是地图的键。
我想把它转换成Map<String, List<String>> result
,它会给我一个每个角色的名单,即
k1: Batsman v1: [Player1, Player2]
k2: Bowler v2: [Player3]
listOfData
.stream()
.map(entry -> new AbstractMap.SimpleEntry<>(entry.get("Role"), entry.get("Name"))
.collect(Collectors.toList());
这样做不会给我一个角色名称列表,它会给我一个名字。如何继续收集列表中的元素,然后将其添加到密钥?
用于创建基础结构的Java代码:
Map<String, String> x1 = ImmutableMap.of("Role", "Batsman", "Name", "Player1");
Map<String, String> y1 = ImmutableMap.of("Role", "Batsman", "Name", "Player2");
Map<String, String> z1 = ImmutableMap.of("Role", "Bowler", "Name", "Player3");
List<Map<String, String>> list = ImmutableList.of(x1, y1, z1);
Map<String, List<String>> z = list.stream()
.flatMap(e -> e.entrySet().stream())
.collect(Collectors.groupingBy(Map.Entry::getKey,
Collectors.mapping(Map.Entry::getValue, Collectors.toList())));
答案 0 :(得分:5)
listOfData.stream()
.flatMap(e -> e.entrySet().stream())
.collect(Collectors.groupingBy(Map.Entry::getKey,
Collectors.mapping(Map.Entry::getValue,
Collectors.toList())));
<强>更新强>
与user1692342
's完全相同的变体略有不同。
list.stream()
.map(e -> Arrays.asList(e.get("Role"), e.get("Name")))
.collect(Collectors.groupingBy(e -> e.get(0),
Collectors.mapping(e -> e.get(1), Collectors.toList())));
答案 1 :(得分:3)
基于Aomine提出的想法:
list.stream()
.map(e -> new AbstractMap.SimpleEntry<>(e.get("Role"), e.get("Name")))
.collect(Collectors.groupingBy(Map.Entry::getKey,
Collectors.mapping(Map.Entry::getValue, Collectors.toList())));
答案 2 :(得分:0)
Map<String, List<Person>> groupByPriceMap = lis.stream().collect(Collectors.groupingBy(Person::getRole));