Question

编辑：这是一个语法问题 - 在发布此版本时已经是一个完整的菜鸟，并且没有使用正确的IDE，所以我向社区道歉。此外，请尽量避免假设本网站上的每个人都是一个人。

我正在和我的内心课DateTest搏斗。编译后出现此错误消息，我无法弄清楚如何修复该错误。我已经通过多行代码来计算测试类，试图打印出Date类中所有12个switch块的情况。

下面我已经包含了错误和我的代码。另外值得一提的是，我正在使用CodeChef中的在线IDE，browxy和双重检查。

这是我的代码：

public class Date {  

    public static int daysInMonth(int month) {  

    /** method uses a switch block and takes in a month number (1 for January, 2 for February, etc.) and returns the number of days in a month. **/  

        switch (month) {  
            case 1:  
            case 3:  
            case 5:  
            case 7:  
            case 8:  
            case 10:  
            case 12:  
                return 31;   
                break;  
            case 2:  
                return 28;  
                break;  
            case 4:  
            case 6:  
            case 9:  
            case 11:  
                return 30;  
                break;  
            default:   
                System.out.println("Invalid month.");  
                break;  
        }  
        return month;  
    }  

    public class DateTest {  

        /*test class that prints out 12 lines like: "January is 31 days long.", "February...", etc.*/   

        int month; /* <-- compilation error had been here due to missing curly brace (error = "class expected") */  
    }  

    public static void main (String [] args) {  
        month = Date.daysInMonth(1);  
        System.out.println("January is " +month+  " days long.");  
        month = Date.daysInMonth(2);  
        System.out.println("February is " +month+ " days long.");  
        month = Date.daysInMonth(3);  
        System.out.println("March is " +month+ " days long.");  
        month = Date.daysInMonth(4);  
        System.out.println("April is " +month+ " days long.");  
        month = Date.daysInMonth(5);  
        System.out.println("May is " +month+ " days long.");  
        month = Date.daysInMonth(6);  
        System.out.println("June is " +month+ " days long.");  
        month = Date.daysInMonth(7);  
        System.out.println("July is " +month+ " days long.");  
        month = Date.daysInMonth(8);  
        System.out.println("August is " +month+ " days long.");  
        month = Date.daysInMonth(9);  
        System.out.println("September is " +month+ " days long.");  
        month = Date.daysInMonth(10);  
        System.out.println("October is " +month+ " days long.");  
        month = Date.daysInMonth(11);  
        System.out.println("November is " +month+ " days long.");  
        month = Date.daysInMonth(12);  
        System.out.println("December is " +month+ " days long.");   
    }  
}

（编辑：这是我在这里提出的第一个问题，刚开始学习Java以及如何完全自己编程 - 我建议任何人开始使用：使用足够体面的计算机来支持基本IDE语法高亮，而不是在线环境/没有这个，因为Java / C ++标点符号可能会让你在不熟悉的时候做恶梦。）

Answer 1

month应该只是main函数中的本地成员。只需在第一次使用时添加类型声明，您应该没问题：

public class DateTest {
    public static void main (String [] args) {
        int month = Date.daysInMonth(1);
        // rest of code comes here
    }
}

Answer 2

不允许内部类具有静态方法。只允许使用静态类和Toplevel类

Answer 3

就这样做：

import java.util.Scanner;

public class Date
{
    public static boolean isLeapYear(int year)
    {
        if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0)
        {

            return true;
        }
        else
        {

            return false;
        }
    }

    public static int daysInMonth(int month, boolean isLeapYear)
    {

        /**
         * method uses a switch block and takes in a month number (1 for
         * January, 2 for February, etc.) and returns the number of days in a
         * month.
         **/

        switch (month)
        {
        case 1:
        case 3:
        case 5:
        case 7:
        case 8:
        case 10:
        case 12:
            return 31;
        case 2:
            if (isLeapYear)
            {
                return 29;
            }
            else
            {
                return 28;
            }
        case 4:
        case 6:
        case 9:
        case 11:
            return 30;

        default:
            System.out.println("Invalid month.");
            break;
        }
        return month;
    }

    /*
     * test class that prints out 12 lines like: "January is 31 days long.",
     * "February...", etc.
     */

    public static void main(String[] args)
    {
        Scanner in = new Scanner(System.in);
        int year = in.nextInt();
        boolean isLeapYear = isLeapYear(year);
        int month = 0;
        month = Date.daysInMonth(1, isLeapYear);
        System.out.println("January is " + month + " days long.");
        month = Date.daysInMonth(2, isLeapYear);
        System.out.println("February is " + month + " days long.");
        month = Date.daysInMonth(3, isLeapYear);
        System.out.println("March is " + month + " days long.");
        month = Date.daysInMonth(4, isLeapYear);
        System.out.println("April is " + month + " days long.");
        month = Date.daysInMonth(5, isLeapYear);
        System.out.println("May is " + month + " days long.");
        month = Date.daysInMonth(6, isLeapYear);
        System.out.println("June is " + month + " days long.");
        month = Date.daysInMonth(7, isLeapYear);
        System.out.println("July is " + month + " days long.");
        month = Date.daysInMonth(8, isLeapYear);
        System.out.println("August is " + month + " days long.");
        month = Date.daysInMonth(9, isLeapYear);
        System.out.println("September is " + month + " days long.");
        month = Date.daysInMonth(10, isLeapYear);
        System.out.println("October is " + month + " days long.");
        month = Date.daysInMonth(11, isLeapYear);
        System.out.println("November is " + month + " days long.");
        month = Date.daysInMonth(12, isLeapYear);
        System.out.println("December is " + month + " days long.");
    }

}

Java：内部测试类编译错误 - 打印所有切换块

3 个答案: