我将如何浓缩这些方法？

Question

I couldn't figure out how to solve this problem using a single isValidPassword method so I broke it down into 3 and got it to work. Can someone explain to me how I could use the code I wrote and if possibly condense it?

Create a program Password that prompts for a password from the user and determines if the password is valid or invalid. There should be a static method isValidPassword that validates the password (String) and returns either true or false. A user has ONLY three tries to enter a valid password. A valid password follows these three rules:

- Must have at least eight characters.
- Must contain ONLY letters and digits.
- Must contain at least two digits.

Use dialog boxes for the program. You must use the String and Character classes for this program. You may NOT use regular expressions. The program only needs to run once.

import javax.swing.JOptionPane;

public class Password {

    public static void main(String[] args) {

        int retryCount = 0;

        while (retryCount < 3) {

            retryCount++;

            String password = JOptionPane.showInputDialog("Please Enter the Password");
            if (CheckPassword(password)) {
                JOptionPane.showMessageDialog(null, "Congrats! Correct Password!");
                break;
            }
            else {

                JOptionPane.showMessageDialog(null, "Sorry, Invalid Password, you tried " + retryCount + " times");

                continue;
            }
        }
    }

    public static boolean CheckPassword(String password) {

        if (password.length() >= 8 & CheckAlphanumeric(password) && Check2digits(password)) {
            return true;
        }
        else {
            return false;
        }

    }

    public static boolean CheckAlphanumeric(String string) {

        for (int i = 0; i < string.length(); i++) {
            char x = string.charAt(i);
            if (x < 0x30 || (x >= 0x3a && x <= 0x40) || (x > 0x5a && x <= 0x60) || x > 0x7a) {
                return false;
            }
        }
        return true;
    }

    public static boolean Check2digits(String string) {

        int count = 0;
        for (int i = 0; i < string.length(); i++) {

            char c = string.charAt(i);
            if (Character.isDigit(c)) {
                count++;
            }

            if (count > 2) {
                return true;
            }

        }
        return false;
    }
}

Answer 1

Lets give a quick code review:

• Read about java naming conventions. Method names go camelCase ; and things that return boolean should be named like isPasswordValid() for example
• What your are doing here is actually a good approach: one should prefer many small methods (that carry good meaningful names!) over having a few large methods (the thing behind is called the "Single Layer of Abstraction" Principle)
• You could read about regular expressions in order to do most of that checking; especially checking for "ascii chars only" is a good candidate there! So even when your assignment says "dont use them"; you might want to learn how to use them. Just for your own learning progress! But as Kayaman pointed out, the Character class has many static helper methods for such checks; so there is no need to implement all of that manually.
• Your code is "logically inconsistent". Your code is validating if some string adheres to certain password rules (minimum length, minimum number of digits). But your messages are implying that this code is checking if a provided password is correct ; like in: user enters his password, and then code checks if that password is known and matching a previously stored password. In that sense: make sure messages and code content are consistent!

Beyond that; a suggestion how to enhance your design for "real world" usage. Thing is: there can be many many different rules that make a password valid . Which might change over time. And typically, you would want to tell your user which of that rules his input is conflicting with. One option to address these concerns:

public interface PasswordValidator {
  public void checkPassword(String password) throws InvalidPasswordException;
}

Then you create various implementations, such as

public class MinimumLengthValidator implements PasswordValidator {
  @Override
  public void checkPassword(String password) throws   InvalidPasswordException {
    if (password.lenght() < 8) {
      throw new InvalidPasswordException("Given password is not long enough; expecting at least 8 characters");
    }
  }

And then, you create instances of those different validator classes; and store them in some array. You iterate the array, and call each validation on its own; and when it fails, you directly receive an exception with a nice message for the user.

As said: the above is meant as inspiration only (and just typed down, so beware of typos).

Answer 2

Look at below code which may fulfill your all requirements-

This is pure java class. you can check logic from the below code.

program edit1 - To specify why password is incorrect.

public class Demo {

    private final int passwordAttempts = 3;
    private int countAttempts = 0;
    private String password;
    private int digitCounter = 0;

    public Demo() {
        init();
    }

    public static void main(String[] args) {
        new Demo();
    }

    private String checkPassword(String pass) {
        if (pass.length() >= 8) {
            if (StringUtils.isAlphanumeric(pass)) {
                char[] toCharArray = pass.toCharArray();
                for (int i = 0; i < toCharArray.length; i++) {
                    char check = toCharArray[i];
                    if(Character.isDigit(check)){
                        digitCounter++;
                    }
                }
                if (digitCounter >= 1) {
                    return "success";
                }else{
                    return "digit";
                }
            }else{
                return "alphanumeric";
            }
        }else{
            return "length";
        }
    }

    private void init() {
        while (countAttempts < passwordAttempts) {
           password = JOptionPane.showInputDialog("Please Enter the Password");
           digitCounter = 0;
           String passwordResult = checkPassword(password);
           if (passwordResult.equals("success")) {
              JOptionPane.showInputDialog("yes you entered correct password...");
           } else if(passwordResult.equals("length")){
              JOptionPane.showInputDialog("password must contain atleast 8 characters...");
           }else if(passwordResult.equals("alphanumeric")){
              JOptionPane.showInputDialog("only alphanumeric password accept...");
           }else if(passwordResult.equals("digit")){
              JOptionPane.showInputDialog("password must contain atleast two digits...");
           }
          countAttempts++;
        }
    }
}

Now only you need to replace JOptionPane.showInputDialog() method with some other method which only specify message because showInputDialog() method prompts input text field also to enter value and we don't want this. I don't have idea any idea about swing.

Based on your comment -

This method returning string values like success,length,alphanumeric,digit ect. and below we are comparing this values with all above in if else if. whenever it get equal that means we have to show length message ,alphanumeric string message ,digit message accordingly.

Dependency -

I'm using maven. following dependency need to add into pom.xml file.

<dependency>
        <groupId>org.apache.commons</groupId>
        <artifactId>commons-lang3</artifactId>
        <version>3.0</version>
</dependency>

If you are not aware about maven then simply download jar file from here and provide in lib folder of your project.