跳出while循環

Question

我的while循環有問題。

如果 while 循環條件為false(when the password is wrong) ，則它工作正常，但是當密碼正確時，它會同時寫入You are logged in和Wrong password 。

我明白為什么會這樣，但我不明白如何解決這個問題。 我需要使用 while 循環，因為這是需要它的學校作業。

import java.util.Scanner;
public class Password {
    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);

        String rightPassword = "Hello123";

        System.out.println("Write your password: ");
        String scan = scanner.nextLine();

        while(scan.equals(rightPassword)){
            System.out.println("You are logged in");
            break;
        }
        System.out.println("Wrong password");
    }

}

Answer 1

你應該做的是：

import java.util.Scanner;
public class Password {
    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);
        String rightPassword = "Hello123";
        String scan="";
        while(true){
             System.out.println("Write your password: ");
             scan = scanner.nextLine();
             if(scan.equals(rightPassword)) {
                 System.out.println("You are logged in");
                 break;         
             } else {
                 System.out.println("Wrong password");
             }
        }
    }
}

在這個過程中，我們有一個無限循環，除非您提供正確的密碼，否則它不會中斷。 您也可以為此添加一些嘗試次數作為破壞條件。

根據I know, it become a infinite loop and that's why i use break. My requirement is that i must use a While loop. I know how to use a if-loop to solve the problem.的評論I know, it become a infinite loop and that's why i use break. My requirement is that i must use a While loop. I know how to use a if-loop to solve the problem. I know, it become a infinite loop and that's why i use break. My requirement is that i must use a While loop. I know how to use a if-loop to solve the problem. 您的解決方案應如下所示：

import java.util.Scanner;
public class Password {
    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);
        String rightPassword = "Hello123";
        System.out.println("Write your password: ");
        while(!rightPassword.equals(scanner.nextLine())) {
            System.out.println("Wrong password");
            System.out.println("Write your password: ");
        }
        System.out.println("You are logged in");
    }
}

Answer 2

您可以使用以下代碼。

    int a=1;
    Scanner scanner = new Scanner(System.in);

    String rightPassword = "Hello123";

    System.out.println("Write your password: ");
    String scan = scanner.nextLine();

    while(scan.equals(rightPassword)){
        System.out.println("You are logged in");
        a=0;
       break;
    }
    if(a==1){
        System.out.println("Wrong password");
    }

Answer 3

without changing your code this will help you.


import java.util.Scanner;
public class Password {
    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);

        String rightPassword = "Hello123";

        System.out.println("Write your password: ");
        String scan = scanner.nextLine();

        while(scan.equals(rightPassword)){
            System.out.println("You are logged in");
            break end;
        }
        System.out.println("Wrong password");
        end:
    }

}

Answer 4

你可能有一些倒退的事情。 檢查錯誤的密碼，而不是循環中的正確密碼，然后再次詢問他們的密碼。 這樣，您將收到來自系統的一條消息，這是一個錯誤的密碼，或者在他們“成功登錄”后收到一條消息。

import java.util.Scanner;
public class Password {
    public static void main(String[] args){
        Scanner scanner = new Scanner(System.in);

        String rightPassword = "Hello123";

        System.out.println("Write your password: ");
        String scan = scanner.nextLine();

        while(!scan.equals(rightPassword)){
            System.out.println("Wrong password. Please try again");
            System.out.println("Write your password: ");
            String scan = scanner.nextLine();
        }
        System.out.println("You are logged in");
    }

}