Multi-valued hashtable in Java

Question

Is it possible to have multiple values for the same key in a hash table? If not, can you suggest any such class or interface which could be used?

Answer 1

As others pointed out, no. Instead, consider using a Multimap which can map many values for the same key.

The Google Collections (update: Guava) library contains one implementation, and is probably your best bet.

Edit: of course you can do as Eric suggests, and store a Collection as a value in your Hashtable (or Map, more generally), but that means writing unnecessary boilerplate code yourself. When using a library like Google Collections, it would take care of the low-level "plumbing" for you. Check out this nice example of how your code would be simplified by using Multimap instead of vanilla Java Collections classes.