Java 如何从地图对象获取列表值
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How to get List value from map object
提问by Miss_Ann
I have object value called "mastervalue" from my hashmap. The mastervalue contain ques_id as key, and an array contain score and answer as value. How to get value of the array only(the score and answer) and return as List.
我的哈希图中有一个名为“mastervalue”的对象值。mastervalue 包含 ques_id 作为键，数组包含 score 和 answer 作为值。如何仅获取数组的值（分数和答案）并作为列表返回。
String maprule = "department == '2' && topic == '1'";
mastervalue = (Map<String, List<String>>) map_master.get(maprule);
System.out.println(mastervalue);
mastervalue print out : {10359=[4, 1], 10365=[1, 1], 10364=[1, 1], 10363=[4, 1], 10362=[3, 1], 10369=[1, 1], 10368=[5, 1]}
主值打印输出：{10359=[4, 1], 10365=[1, 1], 10364=[1, 1], 10363=[4, 1], 10362=[3, 1], 10369=[1, 1], 10368=[5, 1]}
采纳答案by Rogue
Okay:
好的：
public <T> List<T> getValues(Map<?, T> map) {
return new ArrayList<>(map.values());
}
Inlined:
内联：
List<List<String>> list = new ArrayList<>(map_master.values());
Or using the method:
或者使用以下方法：
List<List<String>> list = getValues(map_master);
Alternatively, if you want to put all the values of all the lists into one, just iterate:
或者，如果您想将所有列表的所有值合二为一，只需迭代：
List<String> total = new ArrayList<>();
for (List<String> lis : map_master.values()) {
total.addAll(lis);
}
And with Java 8 streams:
使用 Java 8 流：
List<String> total = map_master.values().stream()
.flatMap(Collection::stream)
.collect(Collectors.toList());
