How do you flush a buffered log4j FileAppender?

In log4j, when using a FileAppender with BufferedIO=true and BufferSize=xxx properties (i.e. buffering is enabled), I want to be able to flush the log during normal shutdown procedure. Any ideas on how to do this?

When shutting down the LogManager:

LogManager.shutdown();

all buffered logs get flushed.

public static void flushAllLogs()
{
    try
    {
        Set<FileAppender> flushedFileAppenders = new HashSet<FileAppender>();
        Enumeration currentLoggers = LogManager.getLoggerRepository().getCurrentLoggers();
        while(currentLoggers.hasMoreElements())
        {
            Object nextLogger = currentLoggers.nextElement();
            if(nextLogger instanceof Logger)
            {
                Logger currentLogger = (Logger) nextLogger;
                Enumeration allAppenders = currentLogger.getAllAppenders();
                while(allAppenders.hasMoreElements())
                {
                    Object nextElement = allAppenders.nextElement();
                    if(nextElement instanceof FileAppender)
                    {
                        FileAppender fileAppender = (FileAppender) nextElement;
                        if(!flushedFileAppenders.contains(fileAppender) && !fileAppender.getImmediateFlush())
                        {
                            flushedFileAppenders.add(fileAppender);
                            //log.info("Appender "+fileAppender.getName()+" is not doing immediateFlush ");
                            fileAppender.setImmediateFlush(true);
                            currentLogger.info("FLUSH");
                            fileAppender.setImmediateFlush(false);
                        }
                        else
                        {
                            //log.info("fileAppender"+fileAppender.getName()+" is doing immediateFlush");
                        }
                    }
                }
            }
        }
    }
    catch(RuntimeException e)
    {
        log.error("Failed flushing logs",e);
    }
}