Java输入某年某月某日，判断这一天是这一年的第几天？

import java.util.GregorianCalendar;
import java.util.Scanner;

public class Test4 {
	
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
				System.out.print("输入年份：");
				int year = scan.nextInt();
				System.out.print("输入月份：");
				int month = scan.nextInt();
				System.out.print("输入日期：");
				int day = scan.nextInt();
				//判断是否是闰年
				//GregorianCalendar:判断年份是否是闰年的方法
				GregorianCalendar gre = new GregorianCalendar();
				boolean isLeapYear=gre.isLeapYear(year);//返回true:是闰年，false：不是闰年
				
				int ap=isLeapYear?29:28;//判断2月份的天数
				int days=0;
				switch (month) {
				case 1:
					days=day;
					break;
				case 2:
					days=31+day;
					break;
				case 3:
					days=31+ap+day;
					break;
				case 4:
					days=31+ap+31+day;
					break;
				case 5:
					days=31+ap+31+30+day;
					break;
				case 6:
					days=31+ap+31+30+31+day;
					break;
				case 7:
					days=31+ap+31+30+31+30+day;
					break;
				case 8:
					days=31+ap+31+30+31+30+31+day;
					break;
				case 9:
					days=31+ap+31+30+31+30+31+31+day;
					break;
				case 10:
					days=31+ap+31+30+31+30+31+31+30+day;
					break;
				case 11:
					days=31+ap+31+30+31+30+31+31+30+31+day;
					break;
				case 12:
					days=31+ap+31+30+31+30+31+31+30+31+30+day;
					break;
		 
				default:
					System.out.println("月份输入错误");
					break;
				}
				System.out.println("这一天是这一年的第"+days+"天");
		}

	
	
}