public static <T> String listToString(T[] lst, String ...format_str) {
        StringBuffer sbuf = new StringBuffer();
        //String format = params==null ? "[,]" : params[0];
        String format = getSingleDefault(format_str, "[,]");
        assert format.length() == 3;
        
        sbuf.append(format.charAt(0));
        for (int i=0; i<lst.length; i++) {
            sbuf.append(lst[i]);
            sbuf.append(format.charAt(1));
        }
        sbuf.setCharAt(sbuf.length()-1, format.charAt(2));
        
        return sbuf.toString();
    }