title: How does my Java logger (say logback) find the line number of my code?
body: <p>how does my Java logger (say logback) find the line number of my code?</p>
  
  <p>Is this a performance issue in a high performance system to include the file line number?</p>
  
  <p>Does it need to throw an exception and analyse the stack trace to do this or is there another trick to this?</p>
  
  <p>thanks</p>