切换案例验证

Question

我正在尝试验证switch case语句，以确保用户没有输入任何字符或字符串类型。我该如何做到这一点？我一直在尝试使用while语句，但是我无法验证它。

public static boolean showMenu()
{
    // Print welcome message
    System.out.println("\nApplication Menu : ");
    System.out.println("[1] Help");
    System.out.println("[2] Add");
    System.out.println("[3] Subtract");
    System.out.println("[4] Multiply");
    System.out.println("[5] Divide");
    System.out.println("[6] Quit");

    int SelectMenu = jin.nextInt();

    switch(SelectMenu)
    {

        case 1:
        showChoice();
        break;

        case 2:
        add();
        break;

        case 3:
        subtract();
        break;

        case 4:
        multiply();
        break;

        case 5:
        divide();
        break;

        case 6:
        return false;

    }
    return true;
}

Answer 1

您可以按如下方式使用循环：

String line = jin.nextLine();
while(!line.matches("\\d")){
    System.out.println("Nope, please enter a digit");
    line = jin.nextLine();
}
int selectMenu  = Integer.parseInt(line);

Answer 2

看一下这个简单的示例，并将其应用到您的代码中：

/**
 *
 * @author Momir Sarac
 */
public class SwitchExample {

    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);
        System.out.println("\nApplication Menu : ");
        System.out.println("[1] Help");
        System.out.println("[2] Add");
        System.out.println("[3] Subtract");
        System.out.println("[4] Multiply");
        System.out.println("[5] Divide");
        System.out.println("[6] Quit");

        while (!scanner.hasNextInt()) scanner.next();
        int number = scanner.nextInt();
        switch (number) {
            case 1:
                clickedHelp();
                break;
            case 2:
                clickedAdd();
                break;
            case 3:
                clickedSubtract();
                break;
            case 4:
                clickedMultiply();
                break;
            case 5:
                clickedDivide();
                break;
            default:
                clickedSomething();

        }

    }

    public static void clickedHelp(){
        System.out.println("Help!");
    }


    public static void clickedAdd(){
        System.out.println("Add");
    }


    public static void clickedSubtract(){
        System.out.println("Subtract");
    }


    public static void clickedMultiply(){
        System.out.println("Multiply");
    }


    public static void clickedDivide(){
        System.out.println("Divide");
    }

    public static void clickedSomething(){
        System.out.println("Exit");
        System.exit(0);
    }

}

Answer 3

我希望你需要做这样的事情

public static boolean showMenu()
{


    while(true) {

        // Print welcome message
        System.out.println("\nApplication Menu : ");
        System.out.println("[1] Help");
        System.out.println("[2] Add");
        System.out.println("[3] Subtract");
        System.out.println("[4] Multiply");
        System.out.println("[5] Divide");
        System.out.println("[6] Quit");

        int SelectMenu = jin.nextInt();

        switch(SelectMenu)
        {

            case 1:
                showChoice();
                break;

            case 2:
                add();
                break;

            case 3:
                subtract();
                break;

            case 4:
                multiply();
                break;

            case 5:
                divide();
                break;

            case 6:
                return false;

        }

    }

}