问如何检查java字符串中是否有5个字母或数字，例如'12345ab'无效？

EN

import java.util.Scanner;

public class Assignment5E3{
  public static void main(String[] args){
  Scanner reader = new Scanner(System.in);
  System.out.println("Please enter a new password: ");
  String password = reader.next();
  String firstRule = ruleOne(password);
  String secondRule = ruleTwo(password);
  String thirdRule = ruleThree(password);
  }
  public static String ruleOne(String password){
    if( password.length() < 5 || password.length() > 12 ){
      System.out.println("Password must be between 5 and 12 characters!");
    }else{
      System.out.println(password);
    }
    return password;
  }
  public static String ruleTwo(String password){
    int j = 0;
    int k = 0;
    for(int i=0; i<password.length(); i++){
      char ch = password.charAt(i);
      if(Character.isLetterOrDigit(ch)){
        j++;
      }else if(!Character.isLetterOrDigit(ch)){
        k++;
      }
    }
    if(k > 0){
      System.out.println("Password may only contain letters and numbers");
    }

    return password;
  }

  public static String ruleThree(String password){
    char[] input = password.toCharArray();
    char[] letters = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz".toCharArray();
    char[] numbers = "0123456789".toCharArray();
    for(int i = 0; i<input.length-1; i++){
      for(int j = 0; j<numbers.length-1; j++){
        if((input[i] == numbers[j+1]) && (input[i+1] == numbers[j+2]) && (input[i+2] == numbers[j+3]) && (input[i+3] == numbers[j+4]) && (input[i+4] == numbers[j+5])){
          System.out.println("Password cannot have 5 numbers in sequence!");
       }
      }
      for(int k = 0; k<letters.length-1; k++){
        if((input[i] == letters[k+1]) && (input[i+1] == letters[k+2]) && (input[i+2] == letters[k+3]) && (input[i+3] == letters[k+4]) && (input[i+4] == letters[k+5])){
          System.out.println("Password cannot have 5 letters in sequence!");
        }
}
}
    return password;
}
}

import java.util.Scanner;

public class Assignment5E3{
  public static void main(String[] args){
  Scanner reader = new Scanner(System.in);
  // receiving input from user to check for password validity
  System.out.println("Please enter a new password: ");
  String password = reader.next();

  // calling first method to check if the password is between 5 and 12 characters
  String firstRule = ruleOne(password);

  // calling second method to check if the password only contains letters and digits
  String secondRule = ruleTwo(password);

  // calling third method to make sure that there is not 5 letters or digits in sequence within the password
  String thirdRule = ruleThree(password);
  }

  // method of rule one, this will check to see if the password is between 5 and 12 characters long
  public static String ruleOne(String password){
    if( password.length() < 5 || password.length() > 12 ){
      System.out.println("Password must be between 5 and 12 characters!");
    }else{
      System.out.println(password);
    }
    return password;
  }

  // method of rule two, this will check to see if the password will only contain letters and digits
  public static String ruleTwo(String password){
    int j = 0;
    int k = 0;
    for(int i=0; i<password.length(); i++){
      char ch = password.charAt(i);
      if(Character.isLetterOrDigit(ch)){
        j++;
      }else if(!Character.isLetterOrDigit(ch)){
        k++;
      }
    }
    if(k > 0){
      System.out.println("Password may only contain letters and numbers");
    }

    return password;
  }

  // method of rule three, this will check to see if the password does not contain 5 letters or digits in sequence
  // within the password
  public static String ruleThree(String password){
    char[] input = password.toCharArray();
    char[] letters = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz".toCharArray();
    char[] numbers = "0123456789".toCharArray();

    // since password length is already greater than 5 chars, I need to -5 in loop so that the index is not out of bounds
    for(int i = 0; i<input.length-5; i++){
      for(int j = 0; j<numbers.length-1; j++){
        if((input[i] == numbers[j+1]) && (input[i+1] == numbers[j+2]) && (input[i+2] == numbers[j+3]) && (input[i+3] == numbers[j+4]) && (input[i+4] == numbers[j+5])){
          System.out.println("Password cannot have 5 numbers in sequence!");
       }
      }
      for(int k = 0; k<letters.length-1; k++){
        if((input[i] == letters[k+1]) && (input[i+1] == letters[k+2]) && (input[i+2] == letters[k+3]) && (input[i+3] == letters[k+4]) && (input[i+4] == letters[k+5])){
          System.out.println("Password cannot have 5 letters in sequence!");
        }
}
}
    return password;
}
}