Java Hashmap: How to get key from value?

Question

If I have the value \"foo\", and a HashMap ftw for which ftw.containsValue(\"foo\") returns true, how can I

Answer 1

It's important to note that since this question, Apache Collections supports Generic BidiMaps. So a few of the top voted answers are no longer accurate on that point.

For a Serialized BidiMap that also supports duplicate values ( 1-to-many scenario ) also consider MapDB.org.