what java collection that provides multiple values for the same key

Question

what type of java collection that returns multiple values for the same key?

example, I want to return 301,302,303 for key 300.

Answer 1

1. As mentioned in a comment above above there is always Guava Multimap
   http://docs.guava-libraries.googlecode.com/git/javadoc/com/google/common/collect/Multimap.html

2. Apache Commons Collections 4 has Generic version of MultiMap http://commons.apache.org/proper/commons-collections/apidocs/org/apache/commons/collections4/MultiMap.html

3. JAX-RS specifies a MultivaluedMap interface which is implemented by all JAX-RS Providers. If your use case is within the context of a JAX-RS REST Service/Client, it would be an option to use their implementation without pulling in another dependency.

   javax.ws.rs.core.MultivaluedMap (each JAX RS Provider has their own implementation)