密码在Java中，通过使用正则表达式的

问题描述：

我试图用正则表达式做一个密码，我不明白为什么我的代码不工作：密码在Java中，通过使用正则表达式的

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. 
    } 
}

纠正“正则表达式”后“regexx”和编译后，当我输入一个完全适用的密码，它仍然会提示密码需要一个大写，它也需要一个数字

你的意思是正则表达式？ – procrastinator

你明白为什么这些行不能编译？ String redex =（^ [0-9] + $）; String redexx =（^ [A-Z] + $）; – Stultuske

'password.length（）> 8'表示密码必须至少有9个字符才能通过该测试，而不是8个，因为您之后写入3行。 –

答

试试这个：

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."); 
    } 
}

除了在你的问题的意见中提到的错误，你也可以使用正则表达式不正确。有关如何在Java中使用正则表达式的信息，请参阅Java regular expression constructs。

此外，空格字符实际上使密码更强，所以我建议允许用户输入空格字符。在我的答案的演示代码中，虽然用户不允许输入空格字符，因为这是您的要求。

答

问题可能是因为你没有把“正则表达式”用引号引起来。他们是字符串。

所以尝试：

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

密码在Java中，通过使用正则表达式的

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