是否有可能转换List<Entry>为Map<Employee, Map<LocalDate, Entry>>一个lambda表达式？
public class Entry {
Employee employee;
LocalDate date;
}
到目前为止,我想出了类似的东西:
entries.stream().collect(Collectors.toMap(Collectors.groupingBy(Entry::getEmployee), Collectors.groupingBy(Entry::getDate), Function.identity()));
但这会产生编译错误:
no suitable method found for
toMap(java.util.stream.Collector<com.a.Entry,capture#1 of ?,java.util.Map<com.a.Employee,
java.util.List<com.a.Entry>>>??,java.util.stream.Co??llector<com.a.Entry,??capture#2 of ?,
java.util.Map<java.time.LocalDate,java.util.List<com.a.Ent?ry>>>,
java.util.func??tion.Function<java.l??ang.Object,java.lang??.Object>)
谢谢