Reversing a HashMap from Map to Map>

Question

Is there a more elegant/built-in way to reverse the keys and values of a Hashmap?

I currently have the following.

private Map

        

Answer 1

You might consider using one of Guava's Multimap implementations. For example:

private Multimap reverseMap(Map permissions) {
   Multimap multimap = ArrayListMultimap.create();
   for (Map.Entry entry : permissions.entrySet()) {
      multimap.put(entry.getValue(), entry.getKey());
   }
   return multimap;
}

Or more generally:

private static  Multimap reverseMap(Map source) {
   Multimap multimap = ArrayListMultimap.create();
   for (Map.Entry entry : source.entrySet()) {
      multimap.put(entry.getValue(), entry.getKey());
   }
   return multimap;
}