title: Check if a Java Set contains a particular string, independent of case
body: <p>I'm trying to test whether a set of strings contains a particular string, independent of case. For example, if mySet contained "john" xor "John" xor "JOHN" xor..., then</p>
  
  <pre><code>mySet.contains("john")
  </code></pre>
  
  <p>(or something similar) should return true.</p>