java入门------（if+switch）判断当天在当年中的天数

import java.util.Scanner;
public class days {
	public static void main(String[] args) {
		Scanner scan=new Scanner(System.in);
		System.out.println("请输入年份：");
		int year=scan.nextInt();
		System.out.println("请输入月份：");
		int month=scan.nextInt();
		System.out.println("请输入日数：");
		int day=scan.nextInt();
		int days=0;
			if ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0)) {	
			days+=0;
			switch (month-1) {
			case 12:
			days+=31;
			case 11:
			days+=30;
			case 10:
			days+=31;
			case 9:
			days+=30;
			case 8:
			days+=31;
			case 7:
			days+=31;
			case 6:
			days+=30;
			case 5:
			days+=31;
			case 4:
			days+=30;
			case 3:
			days+=31;
			case 2:
			days +=29;
			case 1:
			days+=31;
			break;
				} days = days + day;
			}
			else if(month<13&&day<32){	
				days+=0;
				switch (month-1) {
				case 12:
				days+=31;
				case 11:
				days+=30;
				case 10:
				days+=31;
				case 9:
				days+=30;
				case 8:
				days+=31;
				case 7:
				days+=31;
				case 6:
				days+=30;
				case 5:
				days+=31;
				case 4:
				days+=30;
				case 3:
				days+=31;
				case 2:
				days +=28;
				case 1:
				days+=31;
				break;
				default:
						}
						days = days + day;				
			}else {
						System.out.println("你输入的月份有误！");
						} 
			System.out.println("今天是" + year + "年的第" + days + "天");
		}
}