title: Extract Drive Letter, java regex
body: <p>I cannot get this simple regex to work.  I need to check to see if the file path includes the drive letter, if it doesn't throw an exception. </p>
  
  <pre><code>if (!arcvalFileFormBean.getTxtFileReview().matches("^([A-Z]):")) {
      status = "MAPPING ERROR: Please submit a file from a mapped drive (i.e. K:\\).";
      request.setAttribute(FairValConstants.status, status);
      throw new InvalidFileMoveException(FairValConstants.MAKE_VALID_SELECTION);
  }
  </code></pre>
  
  <p>When I test the code with this <code>W:\testFolder\testfile_v1234_12_23_2014_1245.pfd</code> it fails, when it should pass. When I test it without the drive letter, but the full path it fails.  There is something wrong with my regex. I have tried a few different regexs but nothing has worked. </p>
  
  <p>Thanks for your time.</p>