title: Replace sequence of dots with one underscore
body: <p>I have a string holding any number of dots, sometimes also a sequence of dots.</p>
  
  <p>I want to replace every <code>.</code> (dot) by <code>_</code> (underscore) but when there is a sequence of dots, this should also result only in a single underscore.</p>
  
  <p>Any ideas?</p>
  
  <p>I`m using java.</p>