String s = "杭州20170222ax";
Pattern p = Pattern.compile("([0-9].{5,5})");
Matcher m = p.matcher(s);
m.find();
System.out.println(m.group(1));

遍历字符串，str.charAt(i)>=48 && str.charAt(i)<=57判断数字，第一个符合要求的，就是下标

System.out.println( new Scanner("宁波20170222呵呵22").useDelimiter("\\D+").nextInt());

String s = "杭州20170222ax";
char[] chars = s.toCharArray();
for (int i = 0; i < chars.length; i++) {
    if (Character.isDigit(chars[i])) {
        System.out.println(s.substring(i, i + 6));
        break;
    }
}

http://www.cnblogs.com/androi...