title: hashCode uniqueness
body: <p>Is it possible for two instances of <code>Object</code> to have the same <code>hashCode()</code>? </p>
  
  <p>In theory an object's <code>hashCode</code> is derived from its memory address, so all <code>hashCodes</code> should be unique, but what if objects are moved around during GC?</p>