我遇到了一个java登录菜单应用程序的问题

Question

我在大学有一个项目来创建一个登录菜单类型的应用程序。

我是一个非常初学者，所以请忍受我。 我可以请求某人指引我朝着正确的方向前进，因为我已经在这一点上留下了一些空白。

该应用程序没有完成，所以我知道会有更多的需求添加到它，只知道它只是一个非常准系统的应用程序，我期待构建。

选择选项1后，应用程序会通知用户首先更改密码并尝试。更改密码和尝试之后（我是在测试时更改为5），并重新选择选项1，这个错误出现 -

Exception in thread "main" java.lang.RuntimeException: Uncompilable source code - not a statement 
at loginmenu.LoginMenu.loginAttempt(LoginMenu.java:74) 
at loginmenu.LoginMenu.showMenu(LoginMenu.java:34) 
at loginmenu.LoginMenu.loginAttempt(LoginMenu.java:77) 
at loginmenu.LoginMenu.showMenu(LoginMenu.java:34) 
at loginmenu.LoginMenu.main(LoginMenu.java:12) 

这里是代码 -

package loginmenu; 

import java.util.Scanner; 

public class LoginMenu { 

    private static String correctPassword; 
    public static String userPassword; 
    public static int attemptsCounter; 
    public static boolean loggedIn; 

    public static void main(String[] args) { 
     showMenu(); 
     loginAttempt(); 

    } 

    public static void showMenu() 
    // displays a menu and keeps displaying until user chooses the QUIT option 
    { 
     int userChoice; 
     Scanner myScan = new Scanner(System.in); 
     do { 
      System.out.println("1. Login"); 
      System.out.println("2. Change Password"); 
      System.out.println("3. Change Attempts"); 
      System.out.println("4. Quit"); 
      userChoice = myScan.nextInt(); 

      switch (userChoice) { 
      case 1: { 
       System.out.println("You chose to login."); 
       loginAttempt(); 
       break; 
      } 
      case 2: { 
       System.out.println("You chose to change password."); 
       Scanner myNewScan = new Scanner(System.in); 
       System.out.println("Please enter a password."); 
       userPassword = myNewScan.nextLine(); 

       break; 
      } 

      case 3: { 
       System.out.println("You chose to change attempts."); 
       Scanner myNewScan = new Scanner(System.in); 
       System.out.println("Please enter amount of attempts."); 
       attemptsCounter = myNewScan.nextInt(); 
       break; 
      } 
      case 4: { 
       System.out.println("You have quit the program."); 
       break; 
      } 
      default: { 
       System.out.println("Not a valid choice."); 
      } 
      }// closes switch 
     } while (userChoice != 4); 
     myScan.close(); 
     System.out.println("Goodbye."); 
    }// closes showMenu1 

    public static void loginAttempt() 
    { 
     Scanner scan = new Scanner(System.in); 

     while (correctPassword != userPassword) && (attemptsCounter>=5); 
      { 
       System.out.println("Please change password and attempts first."); 
       showMenu(); 
      } 

     if (userPassword == correctPassword) && (attemptsCounter<=5) 
      { 
       System.out.println("You entered the correct password in " + attemptsCounter + " attempts"); 
      } 
     if (attemptsCounter>=6) 
      { 
       System.out.println("You have been locked out."); 
      } 
    } 
} 

Answer 1

修复你的括号和分号分号，不要使用==/!=作为字符串。

while (correctPassword != userPassword) && (attemptsCounter>=5); 

应该

while (!correctPassword.equals(userPassword) && (attemptsCounter>=5)) 

同样的问题，用括号这里：

if (userPassword == correctPassword) && (attemptsCounter<=5) 

Answer 2

这是我对你的问题的办法。

首先，我将密码设置在第一位。

private static String correctPassword = "tommybee"; 

而且，我只能在这种情况下调用showMenu方法。

public static void main(String[] args) { 
    showMenu(); 
} 

您不必在loginAttempt中调用showMenu方法，while语句也会被删除。

public static void loginAttempt() { 
    if (!(userPassword.toLowerCase().equals(correctPassword)) && (attemptsCounter >= 5)) { 
     System.out.println("Please change password and attempts first."); 
    } 

    if ((correctPassword.toLowerCase().equals(userPassword)) && (attemptsCounter <= 5)) { 
     System.out.println("You entered the correct password in " + attemptsCounter + " attempts"); 
    } 

    if (attemptsCounter >= 6) { 
     System.out.println("You have been locked out."); 
    } 
} 

在showMenu方法中，我只使用一个扫描仪类与系统的输入流。 检查the scanner class。

声明一个扫描器类和userChoice变量初始化为4.

Scanner myScan = new Scanner(System.in); 
int userChoice = 4; 

这里是showMenu方法。

public static void showMenu() 
// displays a menu and keeps displaying until user chooses the QUIT option 
{ 

    Scanner myScan = new Scanner(System.in); 
    int userChoice = 4; 

    do { 
     System.out.println("Choose one of the list below"); 
     System.out.println("1. Login"); 
     System.out.println("2. Change Password"); 
     System.out.println("3. Change Attempts"); 
     System.out.println("4. Quit"); 


     if(myScan.hasNextInt()) 
     { 
      userChoice = myScan.nextInt(); 

      switch (userChoice) { 
       case 1: { 
        System.out.println("You choose to login."); 

        System.out.println("Please enter a password."); 

        userPassword = myScan.next(); 
        System.out.println("pass " + userPassword); 
        loginAttempt(); 

        break; 
       } 
       case 2: { 
        System.out.println("You choose to change password."); 
        System.out.println("Please enter a new password."); 
        correctPassword = myScan.next(); 

        break; 
       } 

       case 3: { 
        System.out.println("You choose to change attempts."); 
        System.out.println("Please enter amount of attempts."); 
        attemptsCounter = myScan.nextInt(); 
        break; 
       } 
       case 4: { 
        System.out.println("You have quit the program."); 
        break; 
       } 
       default: { 
        System.out.println("Not a valid choice."); 
       } 
      }// closes switch 
     } 

    } while (myScan.hasNext() && userChoice != 4); 

    myScan.close(); 
    System.out.println("Goodbye."); 

}// closes showMenu1 

我使用下一个方法，而不是nextInt方法。 查看api文档的next method。

在等待要扫描的输入此方法可能阻塞，

这里是我做了什么。

import java.util.Scanner; 

public class LoginMenu { 

    private static String correctPassword = "tommybee"; 
    public static String userPassword; 
    public static int attemptsCounter; 
    public static boolean loggedIn; 

    public static void main(String[] args) { 
     showMenu(); 
     //loginAttempt(); 

    } 

    public static void showMenu() 
    // displays a menu and keeps displaying until user chooses the QUIT option 
    { 

     Scanner myScan = new Scanner(System.in); 
     int userChoice = 4; 

     do { 
      System.out.println("Choose one of the list below"); 
      System.out.println("1. Login"); 
      System.out.println("2. Change Password"); 
      System.out.println("3. Change Attempts"); 
      System.out.println("4. Quit"); 


      if(myScan.hasNextInt()) 
      { 
       userChoice = myScan.nextInt(); 

       switch (userChoice) { 
        case 1: { 
         System.out.println("You choose to login."); 

         System.out.println("Please enter a password."); 

         //Scanner myNewScan = new Scanner(System.in); 
         userPassword = myScan.next(); 
         //myNewScan.close(); 
         System.out.println("pass " + userPassword); 
         loginAttempt(); 

         break; 
        } 
        case 2: { 
         System.out.println("You choose to change password."); 
         //Scanner myNewScan = new Scanner(System.in); 
         System.out.println("Please enter a new password."); 
         correctPassword = myScan.next(); 
         //myNewScan.close(); 

         break; 
        } 

        case 3: { 
         System.out.println("You choose to change attempts."); 
         //Scanner myNewScan = new Scanner(System.in); 
         System.out.println("Please enter amount of attempts."); 
         attemptsCounter = myScan.nextInt(); 
         //myNewScan.close(); 
         break; 
        } 
        case 4: { 
         System.out.println("You have quit the program."); 
         break; 
        } 
        default: { 
         System.out.println("Not a valid choice."); 
        } 
       }// closes switch 
      } 

     } while (myScan.hasNext() && userChoice != 4); 

     myScan.close(); 
     System.out.println("Goodbye."); 

    }// closes showMenu1 

    public static void loginAttempt() { 

     //while ((correctPassword != userPassword) && (attemptsCounter >= 5)) { 
     if (!(userPassword.toLowerCase().equals(correctPassword)) && (attemptsCounter >= 5)) { 
      System.out.println("Please change password and attempts first."); 
      //showMenu(); 
     } 

     if ((correctPassword.toLowerCase().equals(userPassword)) && (attemptsCounter <= 5)) { 
      System.out.println("You entered the correct password in " + attemptsCounter + " attempts"); 
     } 

     if (attemptsCounter >= 6) { 
      System.out.println("You have been locked out."); 
     } 
    } 
}