code: public Object get(Object old)
  	{
  		if (old == null || old.getClass() == String.class)
  		{
  			return old;
  		}
  		return oldNewMap.get(old);
  	}
docs: Gets the new copy of the given old object.
  <p>
  Strings are special objects which have their new copy by default, so if the old object is a string, it is returned directly.
  </p>
  
  @param old
  an old object
  @return the new copy of the given old object, or null if there is not one.