java正则表达式问题？

Question

用正则表达式构造匹配：

1. 密码必须由数字、字符、特殊字符三种同时存在组成；

2. 密码长度不能少于8个字符；

Answer 1

(?!^\d+$)不能全是数字
(?!^[a-zA-Z]+$)不能全是字母
(?!^[_#@]+$)不能全是符号（这里只列出了部分符号，可自己增加，有的符号可能需要转义）
.{8,}长度不能少于8位
合起来就是
(?!^\d+$)(?!^[a-zA-Z]+$)(?!^[_#@]+$).{8,}

Answer 2

After verification, @BodhiXuguang’s answer is incorrect. For example, hello123就能匹配, 但并不满足要求. 而且 8 spaces can also be matched, but it does not meet the requirements, and you cannot add all special symbols.

Although (?=[a-zA-Z0-9_#@]+) can be added to ensure that the password will not contain special symbols other than those specified, there is still no guarantee that it must have three symbols.

Not all numbers/letters/special symbols, the result is as long as it contains more than 2 types of symbols.

In fact, this is not a regular question, please refer to similar questions

Answer 3

List all 6 situations

Answer 4

@BodhiXuguang’s idea is right. Just replace the negative lookahead with a positive lookahead and make some adjustments.
(?=.d.)(?=.[a-zA-Z].)(?=.[_#@].).{8,}

Answer 5

I think this problem should not be solved with regular expressions. Each tool has its own scenarios that are very suitable for use. I think it is not suitable to use regular expressions to solve it in your scenario. Use a simple if statement to judge. The implementation is simple and the readability is very good. Why must we use regular expressions? ?