title: Map of Maps data structure
body: <p>The <a href="http://commons.apache.org/collections/apidocs/org/apache/commons/collections/map/MultiValueMap.html" rel="nofollow noreferrer">MultiValueMap</a> class (Apache commons collections) makes it easy to work with a Map whose values are Collections. I'm looking for a a class that makes it easy to work with a Map whose keys are objects and values are Maps.</p>
  
  <p>I'm using Java 1.4, so can't use Google Collections or generics.</p>