code: public final void fireFileRollEvent(final FileRollEvent fileRollEvent) {
      final Object[] listeners = this.fileRollEventListeners.toArray();
      for (int i = 0; i < listeners.length; i++) {
        final FileRollEventListener listener = (FileRollEventListener) listeners[i];
        listener.onFileRoll(fileRollEvent);
      }
    }
docs: /*
  (non-Javadoc)
  
  @see
  org.apache.log4j.appender.FileRollEventSource#fireFileRollEvent(org.apache
  .log4j.appender.FileRollEvent)