usernamerule ensures that password is not containing the username. consider the following example.

example

import org.passay.passworddata;
import org.passay.passwordvalidator;
import org.passay.rule;
import org.passay.ruleresult;
import org.passay.usernamerule;

public class passayexample {
   public static void main(string[] args) {
      //rule: password should not contain user-name
      rule rule = new usernamerule();
      
      passwordvalidator validator = new passwordvalidator(rule);
      passworddata password = new passworddata("microsoft");
      password.setusername("micro");
      ruleresult result = validator.validate(password);

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

output

invalid password: [password contains the user id 'micro'.]