java - 如何使用正则表达式给出查找头的范围，例如 ^(?=(.*[a-z]){1,3})(?=.*[0-9]).{2,5}$

Question

Question-
1]String length is 2 to 5 
2]String contains at least 1 char and maximum 3 char
3]Atleast one number 

我想使用lookhead。我尝试过但不起作用^(?=(.[a-z]){1,3})(?=.[0-9]).{2,5}$

Answer 1

尝试使用下面的正则表达式

(?=([\\w\\W]{2,5}$))(?=(.*([0-9]){1,}.*))^[^ A-Za-z]*[A-Za-z](?!(?:[^A-Za-z]*[A-Za-z]){3})

public static void main(String[] args) {
    String regex = "(?=([\\w\\W]{2,5}$))(?=(.*([0-9]){1,}.*))^[^A-Za-z]*[A-Za-z](?!(?:[^A-Za-z]*[A-Za-z]){3}).*";

    Pattern pattern = Pattern.compile(regex);
    System.out.println(pattern.matcher("AB2").find()); // output true
    System.out.println(pattern.matcher("AB2C").find()); // output true
}