Looking for Java Map implementation that supports getKeysForValue
<p>I'm looking for an implementation of java.util.Map that has a method that will return all they keys mapped to a given value, that is, there are multiple keys map to the same value.   I've looked at Google Collections and Apache Commons and didn't notice anything.  Of course, I could iterate through the keyset and check each corresponding value or use two maps, but I was hoping there was something available already built.  </p>
