public void flush() {
        for(Flushable opendedFile: wc) {
            try {
                opendedFile.flush();
                if (opendedFile instanceof FileOutputStream) {
                    try {
                        ((FileOutputStream) opendedFile).getFD().sync() ;
                    } catch (java.io.SyncFailedException sfe) {}
                }
            } catch (IOException e) { }
        }
    }