Question

我遇到了do-while循环的问题。它里面有两个if语句。该程序应该使用您的用户名和密码（您输入），然后再次输入它们来确认它们。再次键入时，必须与第一次键入时相同。当布尔重做设置为false时，do-while循环应该停止（当你正确地重新输入你的用户名和密码时它被设置为false）但是循环继续，即使它说你有用户名和密码正确。（它表示欢迎，（用户名））然后循环再次进入，并要求您重新输入您的用户名和密码。在获得正确的密码后如何停止此循环？请帮忙。

package Pack1; 
import java.util.Scanner; 
public class class1 { 
    public static void main(String[] args){

        String Username; //Used to set the original username
        String Password; //Used to set the original password
        String Usernameuse; //Used as a test. This one has to be equal to the original username.
        String Passworduse; //Used as a test. This one has to be equal to the original password.
        boolean redo; //This is to determine whether the do-while loop will repeat.

        Scanner in1 = new Scanner(System.in);  //getting the original username
        System.out.println("Enter your desired username");
        Username = in1.nextLine(); 

        Scanner in2 = new Scanner(System.in); //getting original password
        System.out.println("Enter your desired password");
        Password = in2.nextLine(); 

        System.out.println("Identity Confirmation-- Enter your account information");

        do{
        Scanner in3 = new Scanner(System.in); //gets second username which has to be equal to original
        System.out.println("Please Enter your Username");
        Usernameuse = in3.nextLine(); 

        Scanner in4 = new Scanner(System.in); //gets second password which has to be equal to the original
        System.out.println("Please Enter your Password");
        Passworduse = in4.nextLine();

        if(Usernameuse.equals(Username) && Passworduse.equals(Password)){ //determines if both are true
            System.out.println("Welcome, " + Username);
            redo = false; //makes redo = false
        }
        if(!Usernameuse.equals(Username) || !Passworduse.equals(Password)){ //determines if either one is false
            System.out.println("Either Username or Password are incorrect, please redo");
            redo = true; //makes redo = true
        }

        } while(redo = true); //Is supposed to stop looping when you set redo to false, by entering correct username and password
        System.out.println("You are now on your secret account!"); 
        }
    }

Answer 1

while(redo = true);

这是一项任务而非比较。这将始终为true。

while(redo == true);

是您打算键入的内容，但

while(redo);

是你真正想要的，因为它使得无法提交赋值 - 而不是比较错误。

当你比较boolean以外的常数和变量时，出于同样的原因，最好将常数放在第一位。

if (1 == someInt)

而不是

if (someInt == 1)

如果您不小心使用=而不是==，那么常量优先表单将无法编译。

Answer 2

while(redo = true)

结果始终为true，因为它等于while(true)。

=是作业

==是比较。

为什么我的密码do-while循环在Java中不起作用？我做错了什么？

2 个答案: