fittaoee :
I have the following Java Map, where the values are lists of a custom type (EmployeeInfo):
Map<String, List<EmployeeInfo>> myMap;
My goal is to retrieve all the values as one single List from this map. So far I have tried the following, but haven't made it work yet:
// ERROR: The constructor ArrayList<EmployeeInfo>(Collection<List<EmployeeInfo>>) is undefined
List<EmployeeInfo> info = new ArrayList<EmployeeInfo>(myMap.values());
// ERROR: java.lang.ClassCastException: java.util.HashMap$Values cannot be cast to java.util.List
List<EmployeeInfo> info = (List)myMap.values();
Could anyone provide any help? Thanks in advance!
Sam :
You need to convert the Map<String, List<EmployeeInfo>> or {[e1,e2], [e3,e4]} to List<EmployeeInfo> or [e1,e2,e3,e4]. You can do this by flat mapping the values to list. Here is a approach using streams:
List<EmployeeInfo> list = myMap.values() // gives you [[e1,e2],[e3,e4]]
.stream() // stream over them
.flatMap(List::stream) // convert to [e1,e2,e3,e4]
.collect(Collectors::toList); // collect back
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