新手寻求密码帮助

Question

我正在为我正在进行的项目寻求帮助。我对java比较陌生，正在努力制作一个生成密码的函数。这可能有很多错误，或者这可能是完全错误的，所以请对新手好点>.

import java.util.Random;

public class StillTesting {

    public static void main(String[] args) {
        System.out.println("Your new password is: " + generateValidPassword());
    }

    static private String generateValidPassword() {
        String numcase = "";
        String lowcase = "";
        String upcase = "";
        String halfpass = numcase.concat(upcase);
        String returnString = halfpass.concat(lowcase);

        System.out.print(returnString);

        Random r = new Random();

        String loweralphabet = "abcdefghijklmnopqrstuvwxyz";
        int n = loweralphabet.length();

        String upperalphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
        int N = upperalphabet.length();

        int num = 0;
        for (int i = 0; i < 3; i++) {
            num = r.nextInt(9);

            numcase = String.valueOf(num = r.nextInt(9));
            return numcase;
        }
        for (int i = 0; i < 3; i++) {
            lowcase = String.valueOf(loweralphabet.charAt(r.nextInt(n)));
            return lowcase;
        }
        for (int i = 0; i < 3; i++) {
            upcase = String.valueOf(upperalphabet.charAt(r.nextInt(N)));
            return upcase;
        }
        return returnString;
    }
}

Answer 1

好吧，看起来有几个人在我工作时发现了这些错误，但在我整理完所有内容后，您可能想看看这个工作版本，它解决了原始版本中的大部分问题：

import java.util.Random;

public class StillTesting {

    public static void main( String[] args )
    {
        System.out.println("Your new password is: " + generateValidPassword());
    }

    static private String generateValidPassword()
    {
        StringBuilder password = new StringBuilder();

        Random r = new Random();

        final String loweralphabet = "abcdefghijklmnopqrstuvwxyz";
        final String upperalphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

        for(int i=0;i<3;i++)
        {
            password.append(String.valueOf(r.nextInt(10)));
        }
        for(int i=0;i<3;i++)
        {
            password.append(loweralphabet.charAt(r.nextInt(loweralphabet.length())));
        }
        for(int i=0;i<3;i++)
        {
            password.append(upperalphabet.charAt(r.nextInt(upperalphabet.length())));
        }

        return password.toString();
    }
}

Answer 2

好吧，确实有一些错误：

1. 在分配 numcase、upcase 和 lowcase 的值之前，您正在设置 halfpass 和 returnString 值

2. 您在每个 for 循环的第一次迭代中返回一个值，第一个 return 语句将返回第一个 numcase 值。有关 return 语句如何工作的更多信息here

最后，returnString 语句永远不会到达。

试试这样的：

 static private String generateValidPassword() 
 { 
     String numcase = "";
     String lowcase = "";
     String upcase = "";


     Random r = new Random();

     String loweralphabet = "abcdefghijklmnopqrstuvwxyz";
    int n = loweralphabet.length();

    String upperalphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    int N = upperalphabet.length();

    int num = 0;
    for(int i=0;i<3;i++)
    {
        num=r.nextInt(9);
        numcase += String.valueOf( num = r.nextInt(9));

    }
    for(int i=0;i<3;i++)
    {
        lowcase += String.valueOf(loweralphabet.charAt(r.nextInt(n)));
    }
    for(int i=0;i<3;i++)
    {
        upcase += String.valueOf(upperalphabet.charAt(r.nextInt(N)));
    }
     String halfpass = numcase.concat(upcase);
     String returnString = halfpass.concat(lowcase);

    System.out.print(returnString);
    return returnString;
}
}

Answer 3

您可能想尝试删除循环中的 return 语句，如下所示：

static private String generateValidPassword() 
{ 
    String numcase = "";
    String lowcase = "";
    String upcase = "";
    String halfpass = "";
    String returnString = "";

    System.out.print(returnString);

    Random r = new Random();

    String loweralphabet = "abcdefghijklmnopqrstuvwxyz";
   int n = loweralphabet.length();

   String upperalphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
   int N = upperalphabet.length();

   int num = 0;
   for(int i=0;i<3;i++)
   {
       num=r.nextInt(9);

       numcase = String.valueOf(num);
       returnString += numcase;
   }
   for(int i=0;i<3;i++)
   {
       lowcase = String.valueOf(loweralphabet.charAt(r.nextInt(n)));
       returnString += lowcase;
   }
   for(int i=0;i<3;i++)
   {
       upcase = String.valueOf(upperalphabet.charAt(r.nextInt(N)));
       returnString += upcase;
   }
   return returnString;
 }

这将为您提供类似 637xiqHMR 的输出。您将从每个循环生成的字母组合成一个字符串，然后在最后返回整个字符串，而不是在第一个循环的第一次迭代时返回。

Answer 4

这就是你要找的吗？以下程序的输出类似于433raeWPV 和675croJWV

public static void main(String[] args) {
    System.out.println("Your new password is: " + generateValidPassword());
}

static private String generateValidPassword() {

    String pswd = "";

    Random r = new Random();

    String loweralphabet = "abcdefghijklmnopqrstuvwxyz";
    int n = loweralphabet.length();

    String upperalphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    int N = upperalphabet.length();

    int num = 0;
    for (int i = 0; i < 3; i++) {
        num = r.nextInt(9);

        pswd += String.valueOf(num = r.nextInt(9));
    }
    for (int i = 0; i < 3; i++) {
        pswd += String.valueOf(loweralphabet.charAt(r.nextInt(n)));

    }
    for (int i = 0; i < 3; i++) {
        pswd += String.valueOf(upperalphabet.charAt(r.nextInt(N)));

    }
    return pswd;
}