使用switch语句做到通过键盘输入年月日，输出该日是这一年的第多少天

以下是使用switch语句实现的代码：

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入年份：");
        int year = scanner.nextInt();
        System.out.print("请输入月份：");
        int month = scanner.nextInt();
        System.out.print("请输入日期：");
        int day = scanner.nextInt();

        // 计算该日是这一年的第多少天
        int dayOfYear = 0;
        switch (month) {
            case 1:
                dayOfYear = day;
                break;
            case 2:
                dayOfYear = 31 + day;
                break;
            case 3:
                if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) {
                    dayOfYear = 60 + day;
                } else {
                    dayOfYear = 59 + day;
                }
                break;
            case 4:
                if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) {
                    dayOfYear = 91 + day;
                } else {
                    dayOfYear = 90 + day;
                }
                break;
            case 5:
                if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) {
                    dayOfYear = 121 + day;
                } else {
                    dayOfYear = 120 + day;
                }
                break;
            case 6:
                if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) {
                    dayOfYear = 152 + day;
                } else {
                    dayOfYear = 151 + day;
                }
                break;
            case 7:
                if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) {
                    dayOfYear = 182 + day;
                } else {
                    dayOfYear = 181 + day;
                }
                break;
            case 8:
                if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) {
                    dayOfYear = 213 + day;
                } else {
                    dayOfYear = 212 + day;
                }
                break;
            case 9:
                if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) {
                    dayOfYear = 244 + day;
                } else {
                    dayOfYear = 243 + day;
                }
                break;
            case 10:
                if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) {
                    dayOfYear = 274 + day;
                } else {
                    dayOfYear = 273 + day;
                }
                break;
            case 11:
                if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) {
                    dayOfYear = 305 + day;
                } else {
                    dayOfYear = 304 + day;
                }
                break;
            case 12:
                if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) {
                    dayOfYear = 335 + day;
                } else {
                    dayOfYear = 334 + day;
                }
                break;
            default:
                System.out.println("输入的月份不合法！");
                return;
        }

        System.out.println(year + "年" + month + "月" + day + "日是这一年的第" + dayOfYear + "天。");
    }
}

在上面的代码中，我们使用switch语句根据输入的月份来计算该日是这一年的第多少天。注意，这里需要考虑闰年的情况。如果是闰年，2月份有29天，否则只有28天。其他月份的天数与平年相同。