Question

我用do~while（true）创建了我的菜单;但每次用户插入一个数字，而不是运行程序，它再次显示菜单！你觉得怎么样？

//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
}

// getInput方法

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;
    }
}

Answer 1

因为你有while(true);，这意味着在调用休息之前它将处于无限循环中。

尝试做类似的事情：

 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。

Answer 2

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

while true并不代表你在评论中所写的内容。您需要在while循环中添加一些其他条件来检查该条件。这个条件应该是你从用户那里读到的input。

例如，就像这样。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存在其他一些问题： -

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方法中返回的main()。在那里，您需要将返回值存储在某个局部变量中。

int userInput = displayMenu();

Answer 3

因为你的while循环是while(true)，所以它会一直循环，直到程序被强行破坏。如果没有getInput()函数的内容，可以说的是循环永远不会结束。

您需要使用getInput()方法或使用后处理用户的输入，然后在符合某些条件时有条件地跳出while(true)。

Answer 4

假设你的getInput方法完成了它的说法，那么一旦你的输入被读入，你实际上并没有对你的输入做任何事情。

因此，当用户输入值时，程序会读取该值，请高兴地忽略该值，然后再次运行该菜单。

做Loop同时显示菜单

4 个答案: