code: public static void clearDateFormats(Map<String, DateFormat> copy) {
  	  synchronized(dateFormats) {
  	    if (copy != null) {
  	      copy.putAll(dateFormats);
  	    }
  		dateFormats.clear();
  	  }
  	}
docs: Removes all registered {@link DateFormat DateFormats}.
  
  @param copy if not null, the old values are copied to this map
  @return an unmodifiable version of the original registrations.