如何将 Enum.values() 映射/收集到 HashMap <enum,sortedmap<date,string> &gt; </enum,sortedmap<date,string>

Question

I am trying to make use of the stream API in place of loops, and have the follow problem.

I have a method which takes an Enum and returns a SortedMap. I store each map in a list, however I now wish to now store each SortedMap in a map with the Enum name being the key and the SortedMap returned from listCritieraResults() as the value, how can I do this with the streams API?

Current working List Method

List<SortedMap<Date, String>> collectedMaps = Arrays.stream(Criteria.values())
                                    .map(searcher::listCritieraResults)
                                    .collect(Collectors.toList());

My incorrect attempt to use Collectors.toMap..

Map<String,SortedMap<Date,String>> map = new HashMap<>();

map = Arrays.stream(Criteria.values()).collect(Collectors.toMap(c -> c.name(),c -> searcher.listCritieraResults(c)));

Working loop

Map<Critiera, SortedMap<Date, String>> map = new HashMap<>();

        for ( Criteria criteria : Criteria.values()){
            map.put(criteria.name(),searcher.listCritieraResults(criteria));
        }

Answer 1

Use Map<Criteria,SortedMap<Date,String>> and use Criteria as key in toMap if you want to Criteria as Map's key.

Map<Criteria,SortedMap<Date,String>> map = Arrays.stream(Criteria.values()).collect(Collectors.toMap(c -> c, c -> searcher.listCritieraResults(c)));

Or use string as Map key if you use c.name() in toMap

Map<String ,SortedMap<Date,String>> map = Arrays.stream(Criteria.values()).collect(Collectors.toMap(c -> c.name(), c -> searcher.listCritieraResults(c)));

Answer 2

 HashMap<Criteria,SortedMap<Date,String>> map = new HashMap<>();

map = Arrays.stream(Criteria.values()).collect(Collectors.toMap(c -> c.name(),c -> searcher.listCritieraResults(c)));

In this, you are calling c.name() which will return a string and not Enum Criteria