title: When and why is better to use string format in printing log?
body: <p>I want to print in my log application, using log4j, some value (String, date, ecc).
  For example:</p>
  
  <pre><code>Sting idUser="Test123";
  String name="Jack";
  int age=22;
  
  applicationlog.info("The selected user has this value :\n");
  applicationlog.info("name :"+name+ "id: "+idUser+" age :"+age);
  </code></pre>
  
  <p>But I have sow that in some application there is written:</p>
  
  <pre><code>applicationlog.info(String.format("name :%s id :%s age :%d",name,idUser,age));
  </code></pre>
  
  <p>So my question is :
  When and why is better to use String format instead of "+" only in the print log? I known that with string with concatenation is better to use "+", but I don't thing this is the case, infact here there are only print. 
  Thank you</p>