How to create a Multimap from a Map>?

Question

I didn\'t find such a multimap construction... When I want to do this, I iterate over the map, and populate the multimap. Is there an other way?

final Map<         


        

Answer 1

Here is a useful generic version that I wrote for my StuffGuavaIsMissing class.

/**
 * Creates a Guava multimap using the input map.
 */
public static  Multimap createMultiMap(Map> input) {
  Multimap multimap = ArrayListMultimap.create();
  for (Map.Entry> entry : input.entrySet()) {
    multimap.putAll(entry.getKey(), entry.getValue());
  }
  return multimap;
}

And an immutable version:

/**
 * Creates an Immutable Guava multimap using the input map.
 */
public static  ImmutableMultimap createImmutableMultiMap(Map> input) {
  ImmutableMultimap.Builder builder = ImmutableMultimap.builder();
  for (Map.Entry> entry : input.entrySet()) {
    builder.putAll(entry.getKey(), entry.getValue());
  }
  return builder.build();
}