密碼在Java中，通過使用正則表達式的

Question

我試圖用正則表達式做一個密碼，我不明白爲什麼我的代碼不工作：

import java.util.Scanner; 

class test { 

public static void main (String[] args) { 

    Scanner scanner = new Scanner(System.in); 

    System.out.println("Enter a password please."); 
     String password = scanner.nextLine(); 

    int x; 
    String redex = "(^[0-9]+$)"; 
    String redexx = "(^[A-Z]+$)"; 

    boolean hasSpace = false; 
    boolean hasUpperCase = false; 
     boolean hasLetter = false; 
     boolean hasDigit = false; // we set four booleans to be able to bring up individual error messages. 

    if (password.length() > 8){ 
     hasLetter = true; 
    } else { 
     System.out.println("Your password needs to be at least 8 characters long.");       

     if (password.matches(redexx)) { // we check to see if the password has at least an upper case letter, one or more digits and a space using regular expressions 
      hasUpperCase = true; 

     } if (password.matches(redexx)) { 
      hasDigit = true; 

     } if (password.indexOf(' ') == 1) { 
      hasSpace = true; } 

    } if (hasLetter && hasDigit && hasUpperCase && !hasSpace) { 
     System.out.println("Your password is strong."); 
    } if (!hasDigit) {  
       System.out.println("You need to put numbers in your password."); 
    } if (!hasUpperCase) { 
     System.out.println("You need to use an upper case letter in your password."); 
    } if (hasSpace) { 
        System.out.println("You need to delete any spaces in your password."); 
     } // if we use if statements (and not any "else" or "else if", we get to show all the possible error messages. 
    } 
} 

糾正「正則表達式」後「regexx」和編譯後，當我輸入一個完全適用的密碼，它仍然會提示密碼需要一個大寫，它也需要一個數字

Answer 1

試試這個：

import java.util.Scanner; 

public class Main { 
    public static void main(String[] args) { 
     Scanner scanner = new Scanner(System.in); 
     System.out.println("Enter a password please."); 
     String password = scanner.nextLine(); 

     boolean validLength = password.length() >= 8; 
     boolean hasLetter = password.matches(".*[a-zA-Z].*"); 
     boolean hasDigit = password.matches(".*\\d.*"); 
     boolean hasSpace = password.matches(".*\\s.*"); 

     if (!validLength) 
      System.out.println("The password must be at least 8 characters long."); 
     else if (!hasLetter) 
      System.out.println("The password must contain at least one letter."); 
     else if (!hasDigit) 
      System.out.println("The password must contain at least one digit."); 
     else if (hasSpace) 
      System.out.println("The password must not contain spaces."); 
     else 
      System.out.println("Your password is strong."); 
    } 
} 

除了在你的問題的意見中提到的錯誤，你也可以使用正則表達式不正確。有關如何在Java中使用正則表達式的信息，請參閱Java regular expression constructs。

此外，空格字符實際上使密碼更強，所以我建議允許用戶輸入空格字符。在我的答案的演示代碼中，雖然用戶不允許輸入空格字符，因爲這是您的要求。

Answer 2

問題可能是因爲你沒有把「正則表達式」用引號引起來。他們是字符串。

所以嘗試：

String redex = "(^[0-9]+$)"; 
String redexx = "(^[A-Z]+$)";