title: (String) or .toString()?
body: <p>I have a method with an <code>Object o</code> parameter.</p>
  
  <p>In this method, I exactly know there is a <code>String</code> in "o" which is not null. There is no need to check, or do something else. I have to treat it exactly like a <code>String</code> object.</p>
  
  <p>Just curious - what is cheaper - cast it to <code>String</code>, or use <code>Object.toString()</code>?
  Or is it same by time-/cpu-/mem- price?</p>
  
  <p>Update:
  The method accepts <code>Object</code> because it's the implementation of an interface. There is no way to change the parameter type.</p>
  
  <p>And it can't be <code>null</code> at all. I just wanted to say that I do not need to check it for null or emptyness.  In my case, there is always a nonempty string.</p>