title: Aggregating values in hashmap by keys
body: <p>Consider a simple <code>HashMap&lt;Integer,Integer&gt;</code>. How can I get all the values stored against keys which are multiple of, say 5? I have worked on <code>Java</code> and <code>Collections</code> for some time now, but suddenly I am clueless.</p>
  
  <p>Any help would be highly appreciated.</p>
  
  <p>Regards,</p>
  
  <p>Salil</p>