Java：输入某年某月某日，判断这一天是这一年的第几天？

package com.jredu.ch04;

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

public class Work11 {

public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
System.out.println("输入年份：");
int year = scan.nextInt();
System.out.println("输入月份：");
int month = scan.nextInt();
System.out.println("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");
}

}