title: Java += operator?
body: <p>I originally learned that </p>
  
  <p><code>string += otherString;</code>
  is the same as
  <code>string = string + otherString;</code></p>
  
  <p>However, I found that <code>string += char1 + char2</code> will throw an exception while <code>string = string + char1 + char2</code> will not. When concatenating chars to strings I typically add an empty string so I don't get the exception, but why is that even necessary?</p>