在java中输入某年某月，判断这一天是是这一年的第多少天

package excise;

import java.util.Scanner;

public class T011 {
public static void main(String args[]) {
boolean b = true;
while (b) {
System.out.println("请输入年份：");
Scanner s = new Scanner(System.in);
long date = s.nextLong();
String string_year = String.valueOf(date);
int year = Integer.parseInt(string_year.substring(0, 4));
int month = Integer.parseInt(string_year.substring(4, 6));
int day = Integer.parseInt(string_year.substring(6));

if ((month < 1 || month > 12) || (day < 1 || day > 31)) {
System.out.println("输入年份有错误，请重新输入");
b = true;

} else {
System.out.println("年份输入正确");
b = false;
System.out.println("输入的年份"+date+"是该年的第"+caculate(year,month,day)+"天");
}
}

}

public static int caculate(int year,int month,int day){
int days = 0;
for(int i=1;i<month;i++){
switch(i){
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
days=31;
break;
case 4:
case 6:
case 9:
case 11:
days=30;
break;
case 2:
if((year%400==0)||(year%4==0)||(year%100!=0)){
days=29;
}else{
days=28;
}
break;
default:
break;
}
day+=days;

}
return day;
}

}