Question

当我输入1,2,3以外的错误输入时，我想实现此菜单以保持循环接收输入。如何以及在哪里放置我的while循环/ do while循环？我是JAVA的新人。

用户输入1,2或3以外的菜单后，应再次提示菜单。我可以知道吗？感谢。

如何以及在何处放置while循环/ do while循环？

import java.util.*;
public class InputMenu 
{

public void display_menu() 
{

System.out.println("1) Option 1\n2) Option 2\n3) Option 3");
System.out.print("Selection: ");
}

public void question()
{
System.out.println("Would you like to proceed or quit?");
System.out.println("To proceed enter 9.");
System.out.println("If you wish to quit enter 0.");
Scanner q = new Scanner(System.in);

switch (q.nextInt()) 
{
    case 0:
    System.out.println ("Thank you and goodbye.");
    break;

    case 9:
    System.out.println ("Please proceed.");
    new InputMenu();
    break;
    default:
    System.err.println ( "Unrecognized option" );
        reenter();
    break;
}
}

public void reenter(){
    System.out.println ("Please re-enter option from 1 - 3 only.");
    display_menu();
}

public InputMenu() 
{
Scanner in = new Scanner(System.in);
    display_menu();


switch (in.nextInt()) 
{
    case 1:
    System.out.println ( "You picked option 1" );
    question();
    break;

    case 2:
    System.out.println ( "You picked option 2" );
    question();
    break;

    case 3:
    System.out.println ( "You picked option 3" );
    question();
    break;
    default:
    System.err.println ( "Unrecognized option" );
        reenter();
    break;
}
}

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

Answer 1

可以在您的构造函数

中

public InputMenu() 
{
    Scanner in = new Scanner(System.in);
     display_menu();

    do{       //here
        int input = in.nextInt();
        switch (input) 
        {
            case 1:
            System.out.println ( "You picked option 1" );
            question();
            break;

            case 2:
            System.out.println ( "You picked option 2" );
            question();
            break;

            case 3:
            System.out.println ( "You picked option 3" );
            question();
            break;
            default:
            System.err.println ( "Unrecognized option" );
                reenter();
       }
    }
    while(input>3 || input <1); //here

}

Answer 2

您可以使用以下代码输入valid指定的整数。

public static int read(String hint, Scanner scanner, Integer... valid) {
    System.out.print(hint);
    while (scanner.hasNextLine()) {
        String line = scanner.nextLine();
        try {
            int input = Integer.parseInt(line);
            if (Arrays.asList(valid).contains(input))
                return input;
        } catch (NumberFormatException e) {}
        System.out.print(hint);
    }
    return -1; // This is unreachable
}

然后你打电话

int selection = read("Selection: ", in, 1, 2, 3);

而循环方法Java

2 个答案: