Java8: HashMap to HashMap using Stream / Map-Reduce / Collector

Question

I know how to \"transform\" a simple Java List from Y -> Z, i.e.:

List x;
List y = x.stre         


        

Answer 1

An alternative that always exists for learning purpose is to build your custom collector through Collector.of() though toMap() JDK collector here is succinct (+1 here) .

Map newMap = givenMap.
                entrySet().
                stream().collect(Collector.of
               ( ()-> new HashMap(),
                       (mutableMap,entryItem)-> mutableMap.put(entryItem.getKey(),Integer.parseInt(entryItem.getValue())),
                       (map1,map2)->{ map1.putAll(map2); return map1;}
               ));