Collection assume elements of one value. Map assumes entries of key/value pairs. They could have been engineered to re-use the same common interface however some methods they implement are incompatible e.g.

Collection.remove(Object) - removes an element.
Map.remove(Object) - removes by key, not by entry.

您可以将地图建模为条目集合，这是地图.entrySet（）会。

You could model a Map as a collection of entries, which is what Map.entrySet() does.

有一些共同的方法; size（）， isEmpty（）， ， putAll / addAll（），但是这些不太可能作为独立的接口具有很大的价值。 （可以使用Map.entrySet（））

There are some methods in common; size(), isEmpty(), clear(), putAll/addAll() but these are unlikely to have much value as a stand alone interface. (Again Map.entrySet() can be used instead)