我有一个Map列表,我想使用java流将其按键nom分组。
[
{
"dateDebut": "2018-07-01T00:00:00.000+0000",
"nom": "Julien Mannone",
"etat": "Impayé"
},
{
"dateDebut": "2018-08-01T00:00:00.000+0000",
"nom": "Julien Mannone",
"etat": "Impayé"
},
{
"dateDebut": "2018-10-01T00:00:00.000+0000",
"nom": "Mathiew Matic",
"etat": "payé"
},
{
"dateDebut": "2018-10-01T00:00:00.000+0000",
"nom": "Ash Moon",
"etat": "payé"
}
]
所以我想要这样的结果
{
"Julien Mannone":[
{
"dateDebut":"2018-07-01T00:00:00.000+0000",
"etat":"Impayé"
},
{
"dateDebut":"2018-08-01T00:00:00.000+0000",
"etat":"Impayé"
}
],
"Mathiew Matic":[
{
"dateDebut":"2018-10-01T00:00:00.000+0000",
"etat":"payé"
}
],
"Ash Moon":[
{
"dateDebut":"2018-10-01T00:00:00.000+0000",
"etat":"payé"
}
]
}
作为使用流的初学者,我进行了一些研究,发现了一些类似的代码
Map<String, List<Map>> afterFormatting =
beforeFormatting.stream()
.flatMap(m -> m.entrySet().stream())
.collect(groupingBy(Map.Entry::getKey, mapping(Map.Entry::getValue, toList())));
但这对我没有用
最佳答案
似乎您只是在寻找:
Map<String, List<Map<String, String>>> afterFormatting =
beforeFormatting.stream()
.collect(Collectors.groupingBy(map -> map.get("nom")));
或者,如果您不希望结果集中的每个
Map<String, String>
都包含“nom”条目,则可以执行以下操作:Map<String, List<Map<String, String>>> afterFormatting =
beforeFormatting.stream()
.collect(Collectors.groupingBy(map -> map.get("nom"),
Collectors.mapping(map -> {
Map<String, String> temp = new HashMap<>(map);
temp.remove("nom");
return temp;
}, Collectors.toList())));