code: String getStatistics()
  	{
  		String msg = "PropertyChanges stats :\r\n"
  				+ "# registered handlers : " + nbRegisteredHandlers + "\r\n"
  				+ "# notifications       : " + nbNotifications + "\r\n"
  				+ "# dispatches          : " + nbDispatches + "\r\n";
  		
  		StringBuilder details = new StringBuilder();
  		for( Entry<String, Integer> e : counts.entrySet() )
  		{
  			details.append( e.getKey() + " => " + e.getValue() );
  			
  			Integer oldCount = oldCounts.get( e.getKey() );
  			if( oldCount!=null )
  				details.append( " (diff: " + (e.getValue()-oldCount) + ")" );
  			
  			details.append( "\n" );
  		}
  		
  		oldCounts = new HashMap<>( counts );
  		
  		return msg + details.toString();
  	}
docs: Show an alert containing useful information for debugging. It also
  shows how many registrations happened since last call ; that's useful
  to detect registration leaks.