Java Even Odd Integer 添加是或否问题再次播放

Question

我对 Java 很陌生，正在努力完成一项任务。我已经阅读了几篇文章，但似乎无法弄清楚如何将“Enter·y·to·play·again,·n·to·quit(y/n)”添加到我的代码中。这是我到目前为止所拥有的。任何方向将不胜感激。我不知道如何让它返回输入一个数字。谢了

//Program to display Even or Odd Integer
import java.util.Scanner;

public class EvenOdd {
    public static void main(String[] args) { //method to determine is a number is even or odd
        Scanner input = new Scanner(System.in);
        int number; //number o be entered
        System.out.print("Enter one number: "); //prompt user to enter a number
        number = input.nextInt();
        switch (number % 2) {
            case 0:
                System.out.printf("%d is even\n", number);
            case 1:
                System.out.printf("%d is odd\n", number);
        }
        System.out.print("Enter Y to play again, N to quit: "); //prompt user to enter a number
        number = input.nextInt();
    }

    public boolean isEven(int number) {
        return number %2 == 0;
    } //end method isEven
} //end class EvenOdd

结果：

Enter one number: 1
1 is odd
Enter Y to play again, N to quit: n
Exception in thread "main" java.util.InputMismatchException
    at java.util.Scanner.throwFor(Unknown Source)
    at java.util.Scanner.next(Unknown Source)
    at java.util.Scanner.nextInt(Unknown Source)
    at java.util.Scanner.nextInt(Unknown Source)
    at EvenOdd.main(EvenOdd.java:21)

Answer 1

您得到的异常告诉您输入与您尝试分配的正确类型不匹配。基本上：您正在尝试将类型String（例如“Y”/“N”）分配给int。这将引发错误。在此处阅读有关不同类型的更多信息：https://en.wikibooks.org/wiki/Java_Programming/Primitive_Types

以下是有关如何解决此问题的建议。您还会注意到，我在您的程序中添加了一个 while 循环，以便能够再次播放。 您要更改的代码是input.nextInt() 到input.next()。您还想更改分配给哪个变量，因为您不能将String 分配给int。 还将break; 添加到您的switch 语句中，因此不会遍历每个案例。

public class Main {

    public static void main(String[] args) { //method to determine is a number is even or odd
        String cont = "Y";
        Scanner input = new Scanner(System.in);
        while (cont.equals("Y")) {
            int number; //number o be entered
            System.out.print("Enter one number: "); //prompt user to enter a number
            number = input.nextInt();
            switch (number % 2) {
                case 0:
                    System.out.printf("%d is even\n", number);
                    break; //NOTICE here
                case 1:
                    System.out.printf("%d is odd\n", number);
                    break; //NOTICE here
            }
            System.out.print("Enter Y to play again, N to quit: "); //prompt user to enter a number
            cont = input.next(); // <---- This is what you want 
        }
        System.out.println("Did not want to play again, exiting...");
    }
}