How to merge 2 TreeMap using Stream API (Java 8)?

Question

Java

Hello. Question about Stream API
there are 2 TreeMap

TreeMap<String, String> bar = ...
 TreeMap<String, String> foo = ...

How to combine them?
At what everyone has the same keys, but the values ​​are different. TreeMap after all can store duplicates. After that, I'm going to group by using groupBy( ) from the Stream API.

Answer 1

And, in fact, why are streams here? Map::putAll did not please?
Of course not. Mar is a container of key-value pairs. The key to that and the key is that it is unique.

Answer 2

Map<String, String> myMap = Stream.of(bar, foo)
                                   .map(Map::entrySet)
                                   .flatMap(Collection::stream)
                                   //тут дальше группировка

Tuta