Question

所以我试图让用户输入字符串并检查密码以确保这两件事：

密码至少为8个字符。
密码只包含字母和数字。

现在的问题是：检查密码至少8个字符有效，但检查密码以确保它只包含字母和数字不起作用。如果输入最小数量/字母，它只会在不给出单个消息的情况下终止。 但是，如果它看到的字符不是字母或数字，则会打印出：

请输入密码：###

密码只能包含字母和数字。

密码已被接受！

输出的内容是：

请输入密码：###

密码只能包含字母和数字。

或

请输入密码：test1234

密码已被接受！

    password.java    
    package Password;
    import java.util.Scanner;

    public class Password {

    public static void main(String[]args)
    {

    Scanner input = new Scanner (System.in);
    boolean valid = true;
    System.out.println("Please enter a password:");
    String password = input.nextLine();
    int i = 0;
    //declares i as the counter varible to control the loop and initializes it to 0

    if((password.length( ) < 8 )) //check the passwords length and make sure it's a minimum of 8 characters
    {
    System.out.println("Password must have at least 8 characters.");
    valid = false;
    }
    //loops the code below it for the length of i until the password length is reached
    while(i < password.length())
    {
    if ((password.charAt(i)>='a' && password.charAt(i)<='z') ||  (password.charAt(i)>='A' && password.charAt(i)<='Z') ||(password.charAt(i)>='0' && password.charAt(i)<='9'))
    //loop through all the characters in the string entered and make sure they only consist of letters and numbers
       valid = true;
    else
    {
        System.out.println("Password can only contain letters and numbers.");  
        valid = false;
    }
    i++;
    //add an iteration to the loop
    }

    if(!valid == true)
    System.out.println("Password accepted!");
    }
    }

任何与此有关的帮助都会很棒。

Answer 1

您可以稍微简化一下代码，首先查看valid，然后选择password.length();然后测试密码中的每个字符（如果任何字符无效则停止）。然后在显示接受的消息之前，最后检查密码是否有效。像，

Scanner input = new Scanner(System.in);
System.out.println("Please enter a password:");
String password = input.nextLine();
boolean valid = password.length() >= 8;

if (!valid) {
    System.out.println("Password must have at least 8 characters.");
} else {
    for (char ch : password.toCharArray()) {
        if (!Character.isLetter(ch) && !Character.isDigit(ch)) {
            System.out.println("Password can only contain letters and numbers.");
            valid = false;
            break;
        }
    }
}
if (valid) {
    System.out.println("Password accepted!");           
}

Answer 2

此检查代码中的主要错误是while循环，当您看到错误的字符时无需继续循环时，只需以这种方式执行此类检查：

String toCheck;       //the string to check some criteria 
boolean valid = true; // we assume that nothing wrong happen till now

for(int i=0;i<toCheck.length();i++){ //loop over the characters
    if(/*condition of wrong case*/){ 
        valid = false;               //mark that something wrong happen
        break;                       //exit the loop no need to continue
    }
 }

 if(valid){
    //nothing wrong happen
 } else {
    //something wrong happen
 }

Java检查密码字符串是否有效

2 个答案: