java - For循环在java中显示多个消息框

Question

嘿，我正在创建一个密码验证程序，该程序要求程序检查密码的数字、字母和长度，然后程序比较两个密码以查看它们是否匹配。一切正常，但是当显示错误消息时，它会显示多个消息框。我知道这与 for 循环有关，但我仍然是初学者，我不知道如何解决它。

这是我的代码:

import javax.swing.JOptionPane;

public class Passwords
{
public static void main(String[] args)
{
    String passOne, passTwo;
    passOne = JOptionPane.showInputDialog(null, "Please enter a password");
    passTwo = JOptionPane.showInputDialog(null, "Please re-enter your password");




    //Loop for each digit in password
    for(int x = 0; x < passOne.length(); x++)
    {
        //Testing for a digit
        if(Character.isDigit(passOne.charAt(x)))
            {
                //Testing for a letter
                if(Character.isLetter(passOne.charAt(x)))
                {
                    //Testing length 6-10 chars
                    if(passOne.length() <= 10 && passOne.length() >= 6)
                    {
                        //comparing two passwords
                        if(passOne.equals(passTwo))
                        {
                            JOptionPane.showMessageDialog(null, "Contratulations, you have a new password!");
                        }
                        //If passwords don't match
                        else
                        {
                            JOptionPane.showMessageDialog(null, "Passwords do not match, please try again.");
                        }
                    }
                    //If length is wrong
                    else
                    {
                        JOptionPane.showMessageDialog(null, "Password must be between 6 and 10 characters long.");
                    }
                }
                //If no letter
                else
                {

                    JOptionPane.showMessageDialog(null, "Password must contain at least one letter.");
                }

            }
        //If no digit
        else
            {

                JOptionPane.showMessageDialog(null, "Password must contain at least one digit.");           
            }


    }


}
}

Answer 1

您的代码存在几个问题

1. 您正在迭代密码的字符，但在每次迭代中您都会检查整个密码的长度。您只需在循环之外执行一次。这也适用于检查 passOne 和 passTwo

的相等性

2. “外包”代码来检查数字/字符，如下所示:

   static boolean containsOnlyDigitsOrLetters(String s)
   {
       for(int i = 0; i < s.length; i++)
       {
              if(!(Character.isLetter(s.charAt(i)) || Character.isDigit [...]))
              {
                  // if the current character is neither a letter nor a digit
                  return false;
              }
       }
       // all characters are either digits or letters
       return true;
   }
   

   我特意发布了“仅包含数字和字母”的代码，而不是“至少一位数字”/“至少一个字母”顺便说一句；) 然后，您可以使代码更具可读性，就像这样的伪代码:

   if password's length is not okay:
       display 'at least 6, at max 10'
   else if passwords do not match:
       [...]
   else if password does not contain a letter: // if(!containsAtLeastOneLetter(passOne))
       display 'use at least one letter'
   [....]