Is there a way to get all keys from a value in a multimap?

问题

Say I have a guava Multimap. I have a value, "Foo", that may belong to one or more keys. Is there any way I can figure out which keys contain an entry "Foo"?

回答1:

You can invert the Multimap. For this you can use the method Multimaps.invertFrom.

For example, if your Multimap is a Multimap<String, String>

Multimap<String, String> invertedMultimap = Multimaps.invertFrom(myMultimap, ArrayListMultimap.<String, String>create());

回答2:

If you have an ImmutableMultimap, which is a good idea whenever possible, you can call .inverse().get(v) on it.

来源：https://stackoverflow.com/questions/15031903/is-there-a-way-to-get-all-keys-from-a-value-in-a-multimap