src 字符串截取

实列：

        String str = "http://xx.xxx.xxx.xx/aa/eeee/captcha/img/img_captcha_17a7f2c3-1c56-4c68-a989-ec7ff70bdc66?random=0.12348156695801249";
        int indexOf = str.lastIndexOf("_");
        int endIndexOf = str.lastIndexOf("?");