题目：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 lianxi14 {
public static void main(String[] args) {
int year, month, day;
int days = 0;
int d = 0;
int e;
input fymd = new input();
do {
e = 0;
System.out.print("输入年：");
year =fymd.input();
System.out.print("输入月：");
month = fymd.input();
System.out.print("输入天：");
day = fymd.input();
if (year < 0 || month < 0 || month > 12 || day < 0 || day > 31) {
System.out.println("输入错误，请重新输入！");
e=1 ;
}
}while( e==1);
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;
}
d += days;
}
System.out.println(year + "-" + month + "-" + day + "是这年的第" + (d+day) + "天。");
}
}
class input{
public int input() {
int value = 0;
Scanner s = new Scanner(System.in);
value = s.nextInt();
return value;
}
}