判断一年中第几天

输入某年某月某日，判断这一天是这一年的第几天？

import java.util.*;

public class lianxi09{
    public static void main(String[] args){
        int year = 0, month = 0, day = 0;
        int run = 0, d = 0;
        
        int[] monthday = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
        Scanner sc = new Scanner(System.in);
        while(true){
            System.out.println("请输入年：");
            year = sc.nextInt();
            System.out.println("请输入月：");
            month = sc.nextInt();
            System.out.println("请输入天：");
            day = sc.nextInt();
            if(year < 0 || month <= 0 || month > 12 || day <=0 || day > 31)
                continue;
            break;
        }
        
        if((year % 400) == 0 || (year % 4 == 0 && year % 100 != 0)){
            run = 1;
        }
        
        monthday[2] = monthday[2] + run;
        for(int i = 0; i < month; i++){
            d += monthday[i];
        }
        
        System.out.println(year+"年"+month+"月"+day+"日是这一年的第"+(d + day)+"天");
    }

}