2

我用 do~while(true) 创建了我的菜单；但是每次用户插入一个数字时，它都会再次显示菜单，而不是运行程序！你怎么看？

// 我的主要方法

public static void main(String[] args) {

    DataReader reader = new DataReader(); // The reader is used to read data from a file

    // Load data from the file
    if(reader.loadData(args[0])) {          // The filename is entered using a command-line argument

        vehicles= reader.getVehicleData(); // Store the arrays of Vehicle

        // Display how many shapes were read from the file
        System.out.println("Successfully loaded " + vehicles[0].getCount() + 
                           " vehicles from the selected data file!");
        displayMenu();
    }
}

// 显示菜单方法

private static void displayMenu() {
    Scanner input = new Scanner(System.in);

    do {
        System.out.println("\n\n          Car Sales Menu");
        System.out.println("--------------------------------------");
        System.out.println("1 - Sort vehicles by owner's Last Name");
        System.out.println("2 - Sort vehicles by vehicle Model");
        System.out.println("3 - Sort vehicles by vehicle Cost\n");
        System.out.println("4 - List All Vehicles");
        System.out.println("5 - List All Cars");
        System.out.println("6 - List American Cars Only (Formal)");
        System.out.println("7 - List Foreign Cars only (Formal)");
        System.out.println("8 - List All Trucks");
        System.out.println("9 - List All Bicycles");
        System.out.print("\nSelect a Menu Option: ");
        getInput(input.next()); // Get user input from the keyboard 
    }
    while(true); // Display the menu until the user closes the program
}

// 获取输入法

private static void getInput(String input) {
    switch(Convert.toInteger(input)) {
        case 1: // Sort Vehicles by Owner's Last Name
            Array.sortByOwnerName(vehicles);
            break;
        case 2: // Sort Vehicles by Vehicle Make & Model
            Array.sortByVehicleMakeModel(vehicles);
            break;
        case 3: // Sort Vehicles by Vehicle Cost
            Array.sortByVehicleCost(vehicles);
            break;
        case 4: // List All Vehicles
            displayVehicleData(0);
            break;

        default:
            System.out.print("The entered value is unrecognized!");
            break;
    }
}
4

4 回答 4

3

因为你有while(true);，这意味着菜单将处于无限循环中，直到调用中断。

尝试执行以下操作：

 do {
        System.out.println("\n\n          Car Sales Menu");
        System.out.println("--------------------------------------");
        System.out.println("1 - Sort vehicles by owner's Last Name");
        System.out.println("2 - Sort vehicles by vehicle Model");
        System.out.println("3 - Sort vehicles by vehicle Cost\n");
        System.out.println("4 - List All Vehicles");
        System.out.println("5 - List All Cars");
        System.out.println("6 - List American Cars Only (Formal)");
        System.out.println("7 - List Foreign Cars only (Formal)");
        System.out.println("8 - List All Trucks");
        System.out.println("9 - List All Bicycles");
        System.out.print("\nSelect a Menu Option: ");
    try {
        int input = Integer.parseInt(getInput(input.next())); // Get user input from the keyboard 


        switch (input) {
        case 1:  // do something
                 break;
        case 2:  // do something
                 break;
        ...
       }
      } catch (NumberFormatException e) { ... }

    }
    while(true); // Display the menu until the user closes the program

您可以使用switch来处理输入，并根据输入执行相应的操作。

于 2012-11-23T22:01:52.037 回答
2 
while(true); // Display the menu until the user closes the program

while true并不完全意味着您在评论中写的东西。您需要在 while 循环中添加一些其他条件来检查该条件。这个条件应该是input你从用户那里读到的。

例如，像这样的东西。请注意，这可能无法完全解决您的问题，因为您的代码似乎还有其他一些问题：-

int userInput = 0;
do {
    try {
        userInput = Integer.parseInt(getInput(input.next()));
    } catch (NumberFormatException e) {
        userInput = 0;
    }

} while (userInput < 1 || userInput > 9);

return userInput;  // For this you need to change return type of `displayMenu()`

然后，处理userInput您的方法中返回的 main()内容。在那里，您需要将返回值存储在某个局部变量中。

int userInput = displayMenu();
于 2012-11-23T22:01:48.963 回答
1

因为你的 while 循环是while(true)它会一直循环，直到程序被强制中断。如果没有getInput()函数的内容，只能说循环永远不会结束。

您将需要在方法中或使用后处理用户的输入，然后在满足某些条件时getInput()有条件地突破。while(true)

于 2012-11-23T22:02:57.217 回答
1

假设您的getInput方法按照它所说的那样做，那么一旦您的输入被读入，您实际上并没有对它做任何事情。

因此，当用户输入一个值时，您的程序会读取该值，并愉快地忽略它，然后再次运行菜单。

于 2012-11-23T22:03:09.397 回答