英文:
Convert nested map to nested list
问题
假设我有一个嵌套的 Levels 类，即：
public class Level {
private Map<String, Level> childLevels;
}
我想将这个类转换为如下所示：
public class ListLevel {
private List<ListLevel> childLevels;
}
ChildLevels 可能没有被实例化，并且可能为 null。我从一个 Map<String, Level> 开始，希望通过丢弃每个 Map 条目的键来将其转换为 List<ListLevel>。
我尝试了下面的代码，但还不太行。编辑：下面的代码在使用新的 ListLevel 类时行不通。
private static List<Level> convertToList(Map<String, Level> levelMap) {
return levelMap.values().stream()
.filter(i -> i.getChildLevels() != null)
.flatMap(i -> Stream.concat(Stream.of(i), convertToList(i.getChildLevels()).stream()))
.collect(Collectors.toList());
}
有什么建议吗？
编辑：为了澄清，我想将所有嵌套的映射转换为列表，但保持相同的嵌套结构。
英文:
Assume I have a class Level with nested Levels i.e.
public class Level {
private Map<String, Level> childLevels
}
I want to convert this class into the following:
public class ListLevel {
private List<ListLevel> childLevels
}
ChildLevels are not necessarily instantiated and may be null. I start with a Map<String, Level> and I want to convert this into a List<ListLevel> by discarding the key of every Map entry.
I've tried the code below but it's not quite there. edit: below code won't work with a new ListLevel class
private static List<Level> convertToList(Map<String, Level> levelMap){
return levelMap.values().stream()
.filter(i -> i.getChildLevels() != null)
.flatMap(i -> Stream.concat(Stream.of(i), convertToList(i.getChildLevels()).stream()))
.collect(Collectors.toList());
}
Any suggestions?
edit: to clarify, I want to convert all nested maps to lists but maintain the same nested structure
答案1
得分: 2
你需要使用Map的values()方法，就像levelMap.values().stream()一样，因为你想要获取映射的值。
private static List<Level> convertToList(Map<String, Level> levelMap){
return levelMap.values().stream()
.filter(i -> i.getChildLevels() != null)
.flatMap(i -> Stream.concat(Stream.of(i), convertToList(i.getChildLevels()).stream()))
.collect(Collectors.toList());
}
在问题更新后：
private static List<ListLevel> convertToList(Map<String, Level> levelMap){
if(levelMap == null) return null;
return levelMap.values().stream()
.map(i -> convertLevelToListLevel(i, convertToList(i.getChildLevels())))
.collect(Collectors.toList());
}
这里的ListLevel convertLevelToListLevel(Level level, List<ListLevel> childListLevels)是将Level转换为ListLevel的转换器，正如在评论中提到的。
英文:
You need to use values() of Map like levelMap.values().stream() since you want the values of map.
private static List<Level> convertToList(Map<String, Level> levelMap){
return levelMap.values().stream()
.filter(i -> i.getChildLevels() != null)
.flatMap(i -> Stream.concat(Stream.of(i), convertToList(i.getChildLevels()).stream()))
.collect(Collectors.toList());
}
After question Updated:
private static List<ListLevel> convertToList(Map<String, Level> levelMap){
if(levelMap == null) return null;
return levelMap.values().stream()
.map(i -> convertLevelToListLevel(i, convertToList(i.getChildLevels())))
.collect(Collectors.toList());
}
Here ListLevel convertLevelToListLevel(Level level, List<ListLevel> childListLevels) is converter for Level to ListLevel conversion as mention in comment OP already have.
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