title: Easiest way of checking if a string consists of unique letters?
body: <p>I need to check in Java if a word consists of unique letters (case insensitive). As straight solution is boring, I came up with:</p>
  
  <ol>
  <li>For every char in a string check if <code>indexOf(char) == lastIndexOf(char)</code>.</li>
  <li>Add all chars to <code>HashSet</code> and check if set size == string length.</li>
  <li>Convert a string to a char array, sort it alphabetically, loop through array elements and check if <code>c[i] == c[i+1]</code>.</li>
  </ol>
  
  <p>Currently I like #2 the most, seems like the easiest way. Any other interesting solutions?</p>