Java Regex User specific characters to be allowed -

i trying use regex, allow user specific given password.

i tried not working

^[a-za-z0-9@\\#$%&*()_+\\]\\[';:?.,!^-]{"+min_length+","+max_length+"}$ 

the min_length , max_length database working min , max lenth case, how can give specific uppercase, lowercase, numeric , special characters.

regards pradeep

i'm afraid regexes aren't powerful. find solution using single regex, totally unreadable , unscalable. suggest separate each constraint logic subregex. example:

public static boolean ispasswordvalid(string password) {     // 1 3 occurrences of lowercased chars     if (!password.matches("(?:[^a-z]*[a-z]){1,3}[^a-z]*")) {         return false;     }     // 2 4 occurrences of uppercased chars     if (!password.matches("(?:[^a-z]*[a-z]){2,4}[^a-z]*")) {         return false;     }     // 3 5 occurrences of digits     if (!password.matches("(?:[^0-9]*[0-9]){3,5}[^0-9]*")) {         return false;     }     // 4 6 occurrences of special chars (simplified "_", "." or "-")     if (!password.matches("(?:[^_.-]*[_.-]){4,6}[^_.-]*")) {         return false;     }     // no other kind of chars, , password length 3 20     if (!password.matches("[a-za-z0-9_.-]{3,20}")) {         return false;     }     return true; }