public static void main(String args[]) {
        if (args.length == 0) {
            System.out.println("Usage: java -cp .:../dist/* myutl.MyXlsx {input xlsx file} [output.xlsx]");
            System.exit(0);
        }
        String fn = args[0];
        Map<String, List<String[]>> m = getWkbkData(fn);
        if (m != null) { 
            for (String key: m.keySet()) {
                List<String[]> l = (List<String[]>)m.get(key);
                System.out.println(key + ": " + l.size());
                for (String[]s : l) {
                    boolean f = false;
                    for(String t: s) {
                        if (f) System.out.print(",");
                        else f = !f;
                        System.out.print(t);
                    }
                    System.out.println("");
                }
            }
            if (args.length > 1) { 
                fn = args[1]; 
                if (saveXslx(fn,m))
                    System.out.println(fn + " is successfully written");
            }
        }
    }