title: Logger slf4j advantages of formatting with {} instead of string concatenation
body: <p>Is there any advantage of using <code>{}</code> instead of string concatenation?</p>
  
  <p>An example from slf4j</p>
  
  <pre><code>logger.debug("Temperature set to {}. Old temperature was {}.", t, oldT);
  </code></pre>
  
  <p>instead of</p>
  
  <pre><code>logger.debug("Temperature set to"+ t + ". Old temperature was " + oldT);
  </code></pre>
  
  <p>I think it's about speed optimization because parameters evaluation (and string concatenation) could be avoided in runtime depending on a config file. But only two parameters are possible, then sometimes there is no other choice than string concatenation. Needing views on this issue.</p>