title: StringBuilder constructor accepts a StringBuilder object - why?
body: <p>The class <code>StringBuilder</code> defines four constructors, and none of them accepts a <code>StringBuilder</code>, yet the following compiles:</p>
  
  <pre><code>StringBuilder sb = new StringBuilder(new StringBuilder("Hello"));
  </code></pre>
  
  <p>Does this mean that the anonymous <code>StringBuilder</code> object gets somehow converted to a String internally by the compiler?</p>