一、代码

    /**
     * 截取指定长度的字符串
     * @param str
     * @param maxLength
     * @return
     */
    private static String substring(String str, Integer maxLength) {
        if (StringUtils.isBlank(str)) {
            return null;
        }

        str = str.trim();
        if (null == maxLength || maxLength < 0) {
            return str;
        }

        int length = str.length();
        maxLength = maxLength > length ? length : maxLength;

        return str.substring(0, maxLength);
    }

二、运行结果