title: Match any unicode Letters with java regex
body: <p>I need to match any letters (like MS Office Word find with special character ^$ functionality) with regex.
  I've tried with <code>[a-zA-Z]</code> but don't match any unicode letters like accent letters or ä, ö, ü, ß. 
  I've tried also with <code>[a-zA-ZäöüßÄÖÜ]</code>but there are too many letters. 
  Is there any regex to match all this letters? </p>