characterrule helps in defining a set of characters and minimum no. of characters required in a password.

example

the below example shows the validation of a password against above policy using passay library.

import java.util.arraylist;
import java.util.list;

import org.passay.characterrule;
import org.passay.englishcharacterdata;
import org.passay.lengthrule;
import org.passay.passworddata;
import org.passay.passwordvalidator;
import org.passay.rule;
import org.passay.ruleresult;
import org.passay.whitespacerule;

public class passayexample {
   public static void main(string[] args) {
        
      list<rule> rules = new arraylist<>();        
      //rule 1: password length should be in between 
      //8 and 16 characters
      rules.add(new lengthrule(8, 16));        
      //rule 2: no whitespace allowed
      rules.add(new whitespacerule());        
      //rule 3.a: at least one upper-case character
      rules.add(new characterrule(englishcharacterdata.uppercase, 1));        
      //rule 3.b: at least one lower-case character
      rules.add(new characterrule(englishcharacterdata.lowercase, 1));        
      //rule 3.c: at least one digit
      rules.add(new characterrule(englishcharacterdata.digit, 1));        
      //rule 3.d: at least one special character
      rules.add(new characterrule(englishcharacterdata.special, 1));

      passwordvalidator validator = new passwordvalidator(rules);        
      passworddata password = new passworddata("microsoft@123");        
      ruleresult result = validator.validate(password);

      if(result.isvalid()){
         system.out.println("password validated.");
      } else {
         system.out.println("invalid password: " + validator.getmessages(result));            
      }
   }
}

output

password validated.