class CollectionUtils {

    public static String toString(Collection<?> col) {
        if (isEmpty(col)) {
            return "";
        }
        StringBuilder sb = new StringBuilder();
        sb.append("[");
        for (Object obj : col) {
            sb.append(StringUtils.toString(obj));
            sb.append(",");
        }
        sb.deleteCharAt(sb.length() - 1);
        sb.append("]");
        return sb.toString();
    }

    private  CollectionUtils();

}