title: Java case-insensitive map with null key
body: <p>Is there a Map implementation in Java that will use <strong>case-insensitive</strong> String matching for the key, <strong>but also supports the null key</strong>?
  I know that</p>
  
  <pre><code>new TreeMap&lt;String, String&gt;(String.CASE_INSENSITIVE_ORDER)
  </code></pre>
  
  <p>supports case-insensitive matching of String keys, but it doesn't support the null key.</p>