Question

每当我输入密码时，无论是有效格式还是格式无效，它都会输出＆＃34;密码无效＆＃34;。

   import java.util.Scanner;
    public class PasswordTest
    {
       public static void main (String[] args)
       {
          Scanner input = new Scanner(System.in);
          boolean length = true;
          boolean digit = true;
          boolean lowercase = true;
          boolean uppercase = true;
          char ch = 0;
          String s1;

       //Prompt user to enter password
          System.out.print("Enter password: ");
          s1 = input.nextLine();

       //Check what ch is
          for (int i=0; i<s1.length(); i++){
             ch = s1.charAt(i);

             if (Character.isDigit(ch)){
                digit = true;
             }
             if (Character.isLowerCase(ch)){
                lowercase = true;
             }    
             if (Character.isUpperCase(ch)){
                uppercase = true;
             }
             if (s1.length()>=8){
                length = true;
             }
          }

          if (digit==false && lowercase==false && uppercase==false && length==false)
             System.out.println("Valid password");

          else
             System.out.println("Invalid password");

       }
    }

Answer 1

您需要在声明时首先将所有布尔值设置为false，然后在下面的代码中将其设置为true，只要它满足条件。同时打印“有效密码”时，检查所有布尔值是否为true，否则打印“无效密码”。检查字符串长度是否大于8应该在循环体外。以下代码有效。

import java.util.Scanner;
public class PasswordTest
{
   public static void main (String[] args)
   {
      Scanner input = new Scanner(System.in);
      boolean length = false;
      boolean digit = false;
      boolean lowercase = false;
      boolean uppercase = false;
      char ch=0;
      String s1;

   //Prompt user to enter password
      System.out.print("Enter password: ");
      s1 = input.nextLine();

   //Check what ch is
      for (int i=0; i<s1.length(); i++){
         ch = s1.charAt(i);

         if (Character.isDigit(ch)){
            digit = true;
         }
         if (Character.isLowerCase(ch)){
            lowercase = true;
         }    
         if (Character.isUpperCase(ch)){
            uppercase = true;
         }             
      }
      if (s1.length()>=8){
          length = true;
       }

      if (digit==true && lowercase==true && uppercase==true && length==true)
         System.out.println("Valid password");

      else
         System.out.println("Invalid password");

   }
}

Answer 2

我有一个问题，如果它不能是小写的，如果它不能大写那么它会是什么？我做了它所以它必须是小写的，这里是代码（如果你想要全部大写，那么将代码if(digit[i] == true || lowercase[i] == false || uppercase[i] == true)中的if语句更改为if(digit[i] == true || lowercase[i] == true || uppercase[i] == false)

import java.util.Scanner;

public class PasswordTest{

    public static void main (String[] args){
        Scanner input = new Scanner(System.in);
        boolean length;
        boolean pass = true;
        String s1;

       //Prompt user to enter password
        System.out.print("Enter password: ");
        s1 = input.nextLine();
        boolean[] digit = new boolean[s1.length()];
        boolean[] lowercase = new boolean[s1.length()];
        boolean[] uppercase = new boolean[s1.length()];
        char[] ch = new char[s1.length()];
       //Check what ch is
        for (int i=0; i<s1.length(); i++){
            ch[i] = s1.charAt(i);
            digit[i] = Character.isDigit(ch[i]);
            lowercase[i] = Character.isLowerCase(ch[i]);
            uppercase[i] = Character.isUpperCase(ch[i]);

          }
        length = s1.length()>=8;
        if (length==false && s1.length() > 0) {
            int i;
            for(i = 0; i < s1.length(); i ++){
                if(digit[i] == true|| lowercase[i] == false|| uppercase[i] == true)
                    pass = false;
            }
            if(pass == true)
                System.out.println("Valid password");
            else{
                System.out.println("Invalid password");
            }
        }else{
            System.out.println("Invalid password");
        }

       }
    }

Answer 3

你所做的是首先将布尔值设置为true然后再次在循环中将其设置为true，这没有意义。我认为此代码可以正常工作

        Scanner input = new Scanner(System.in);
        boolean length = false;
        boolean digit = false;
        boolean lowercase = false;
        boolean uppercase = false;
        char ch = '\u0000';
        String s1;

        //Prompt user to enter password
        System.out.print("Enter password: ");
        s1 = input.nextLine();

        //Check what ch is
        for (int i=0; i<s1.length(); i++){
            ch = s1.charAt(i);

            if (Character.isDigit(ch)){
                digit = true;
            }
            if (Character.isLowerCase(ch)){
                lowercase = true;
            }
            if (Character.isUpperCase(ch)){
                uppercase = true;
            }
            if (s1.length()>=8){
                length = true;
            }
        }

        if (digit==true && lowercase==true && uppercase==true && length==true)
            System.out.println("Valid password");

        else
            System.out.println("Invalid password");

Answer 4

对于未来，我认为regular expressions会有所帮助。

您的密码要求似乎是＆＃34;长度为8个或更多字符，其中每个字符可以是小写字母，大写字母或数字，＆＃34;是对的吗？我们可以使用正则表达式表达这些要求，例如([a-z]|[A-Z]|[0-9]){8,}。有了这个，我们可以写

String password = input.nextLine();

if(password.matches("([a-z]|[A-Z]|[0-9]){8,}") {
    // Go about your business.
}

需要创建一个使用循环来检查密码是否正确的java程序。程序运行但输出不正确

4 个答案: