title: Java Map with keys of 3 columns
body: <p>I need a map in which my key should be based on 3 columns, say <code>C1, C2, C3</code>. <code>C1</code> has highest priority. <code>C2</code> has one less than <code>C1</code> and <code>C3</code> has one less than <code>C2</code>.</p>
  
  <p>How do i create key in the map such that if somebody asks for information on <code>C1</code>, I should able to give all the values which has <code>C1</code>. I also should be able to return all the values if asked for <code>C1 &amp; C2</code></p>