Question

我的程序编译，但我得到运行时异常，不确定我是否需要处理它们？注释掉的方法和扩展类，它们只显示文本。我也不知道我是否正确使用标签？我希望我的程序循环并处理错误字符的异常，但它只应在用户输入“5”时终止。

import java.util.*;
import java.util.InputMismatchException;
import java.util.Scanner;


public class Mainmenu3 {

// extends premierLeagueClubs



public static void main(String args[]){

    boolean shouldExit = false;

    int option = 0;
loop:   while (!shouldExit) {
try{
    Scanner in = new Scanner(System.in);     

    menu();
    System.out.println("\n");
    option = in.nextInt();
} // end try

catch(InputMismatchException e) {
String option2 = Integer.toString(option);

    } // end catch

    switch (option) {

    case 1:
    chooseTeam();
    break;

    case 2: 
    createProfile();
    break;

    case 3:
    loadSave();
    break;

    case 4:
    credits();  
    break;

    case 5:
    break loop;

    default:
    System.out.println("Invalid choice");
}

    } // end switch




   } // end main method

public static void chooseTeam(){
System.out.println("\n\n\n\n\n\n\n\n\n\n\n\n\n\n");
System.out.println("Select Team : ");
System.out.println("1. Arsenal");
System.out.println("2. Aston Villa");
System.out.println("3. Bournemouth");
System.out.println("4. Chelsea");
System.out.println("5. Crystal Palace");
System.out.println("6. Everton");
System.out.println("7. Leicester City");
System.out.println("8. Liverpool");
System.out.println("9. Manchester United");
System.out.println("10. Manchester City");
System.out.println("11. Newcastle United");
System.out.println("12. Norwich City");
System.out.println("13. Southampton");
System.out.println("14. Stoke City");
System.out.println("15. Sunderland");
System.out.println("16. Swansea City");
System.out.println("17. Tottenham Hotspur");
System.out.println("18. Watford");
System.out.println("19. West Brom");
System.out.println("20. West Ham United");

int option = 0;

    Scanner in = new Scanner(System.in);
    //menu();

    System.out.println("\n");
    option = in.nextInt();
    System.out.println("You entered : " + option);

} // end chooseTeam



public static void createProfile(){
} // end createProfile
public static void loadSave(){
} // end loadSave
public static void credits(){
} // end credits


public static void menu(){



System.out.println("\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n");
    System.out.println("Created by Darren Estcourt");   
    System.out.println("\n");
    System.out.println("Please choose an option : ");
    System.out.println("\n");
    System.out.println("1. Choose team");
    System.out.println("\n");
    System.out.println("2. Create profile");
    System.out.println("\n");
    System.out.println("3. Load/Save game");
    System.out.println("\n");
    System.out.println("4. Credits");   
    System.out.println("\n");
    System.out.println("5. Quit");

    System.out.println("\n");

    String option="0";

    Scanner in = new Scanner(System.in);

    System.out.println("\n");
    option = in.nextLine();

    switch (option) {

    case "1":
    chooseTeam();
    break;

    case "2":   
    createProfile();
    break;

    case "3":
    loadSave();
    break;

    case "4":
    credits();  
    break;

    case "5":
    System.out.println("Goodbye!"); 

    default:
    System.out.println("Please select an option between 1 and 4");
//menu();
    } // end switch



} // end menu




} // end class

Answer 1

您的计划存在多个问题：

您定义了shouldExit但是根据用户输入更新它
您可以在main（）和menu（）中扫描和处理用户输入。通常，您的代码不是以连贯的可读方式构建的，并且几乎没有重用。
println()已经打印了一个新行（而不是print()）
对编程女神的热爱 - 不使用System.exit（）来终止Java程序

这是一个工人阶级的例子，上面的指导方针是以适用的程度实施的：

import java.util.*;

public class Mainmenu3
{
    static Scanner in;

    public static void main(String args[])
    {
        in = new Scanner(System.in);
        boolean shouldExit = false;
        while (!shouldExit) {
            displayMenu();
            shouldExit = processUserInput();
        }
    }

    public static void displayMenu()
    {
        System.out.println();
        System.out.println("Created by Darren Estcourt");
        System.out.println("Please choose an option : ");
        System.out.println("1. Choose team");
        System.out.println("2. Create profile");
        System.out.println("3. Load/Save game");
        System.out.println("4. Credits");
        System.out.println("5. Quit");
    }

    public static int getUserInput()
    {
        int option = -1;
        try {
            option = in.nextInt();
        } catch (InputMismatchException e) {
            // When a scanner throws an InputMismatchException, 
            // the scanner will not pass the token that caused the exception,
            // so that it may be retrieved or skipped via some other method.
            in.next();
        } catch (NoSuchElementException e) {
            // input is exhausted
            option = 5;
        } catch (IllegalStateException e) {}
            // scanner is closed
            option = 5;
        }
        return option;
    }

    public static boolean processUserInput()
    {
        int option = getUserInput();
        switch (option) {
        case 1:
            chooseTeam();
            break;
        case 2:
            createProfile();
            break;
        case 3:
            loadSave();
            break;
        case 4:
            credits();
            break;
        case 5:
            System.out.println("Goodbye!");
            return true;
        default:
            System.out.println("Invalid choice");
        }
        return false;
    }

    public static void chooseTeam()
    {
        System.out.println();
        System.out.println("Select Team : ");
        System.out.println("1. Arsenal");
        System.out.println("2. Aston Villa");
        System.out.println("3. Bournemouth");
        System.out.println("4. Chelsea");
        System.out.println("5. Crystal Palace");
        System.out.println("6. Everton");
        System.out.println("7. Leicester City");
        System.out.println("8. Liverpool");
        System.out.println("9. Manchester United");
        System.out.println("10. Manchester City");
        System.out.println("11. Newcastle United");
        System.out.println("12. Norwich City");
        System.out.println("13. Southampton");
        System.out.println("14. Stoke City");
        System.out.println("15. Sunderland");
        System.out.println("16. Swansea City");
        System.out.println("17. Tottenham Hotspur");
        System.out.println("18. Watford");
        System.out.println("19. West Brom");
        System.out.println("20. West Ham United");

        int option = getUserInput();

        System.out.println("You entered : " + option);
    } // end chooseTeam

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

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

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

java.util.NoSuchElementException：找不到行，我是否需要处理此异常？

1 个答案: