title: Invalid escape sequence (valid ones are \b \t \n \f \r \" \' \ )
body: <p>I have a problem with a regex in java. </p>
  
  <p>When I try to use this regex: </p>
  
  <pre><code> ^(?:(?:([01]?\d|2[0-3]):)?([0-5]?\d):)?([0-5]?\d)$  
  </code></pre>
  
  <p>I get the following error   </p>
  
  <pre><code>"Invalid escape sequence (valid ones are \b \t \n \f \r \" \' \ )"  
  </code></pre>
  
  <p>I don't know how to handle that error.
  I already tried to double the backslashes, but it didn't work. 
  I hope someone can help me with this. </p>
  
  <p>Thanks </p>