title: duplicate key value pairs
body: <p>Is there a native data structure in java that accepts key value pairs and allows duplicates? I am creating a checklist of characters in a string but some characters occur more than once. </p>
  
  <p>ex</p>
  
  <pre><code>j -&gt; false
  a -&gt; false
  v -&gt; false
  a -&gt; false
  </code></pre>