// 判断字符串是否同时有字母和数字，且不指定以字母或数字开头
public static boolean isLetterAndDigital(String content) {

    String regEx ="([a-z]+\\d+:+)";

    Pattern pattern1 = Pattern.compile(regEx);

    Matcher matcher1 = pattern1.matcher(content);

    boolean flag1 =false;

    while (matcher1.find()) {

        System.out.println(matcher1.group(0));

        flag1 =true;

        break;

    }

    System.out.println(flag1);

    String regEx2 ="(\\d+[a-z]+:+)";

    Pattern pattern2 = Pattern.compile(regEx2);

    Matcher matcher2 = pattern2.matcher(content);

    boolean flag2 =false;

    while (matcher2.find()) {

    System.out.println(matcher2.group(0));

        flag2 =true;

        break;

    }

    System.out.println(flag2);

    return flag1 || flag2;
}

// 执行
public static void main(String[] args) {

    String content ="aaaaf11:aaaaf11:aaaaf11:aaaaf11:";

    System.out.println(isLetterAndDigital(content));
}