50道Java习题之14

import java.util.Scanner;
public class Problem_14 {
public static void main(String[] args) {
int days = 31, flag = 1, sum = 0;
int year = 0, month = 0, day = 0;
Scanner sc = new Scanner(System.in);
while (flag == 1) {
flag = 0;
System.out.print("输入年：");
year = sc.nextInt();
System.out.println("输入月：");
month = sc.nextInt();
System.out.println("输入日：");
day = sc.nextInt();
if (year < 0 || month < 0 || month > 12 || day < 0 || day > 31) {
System.out.println("输入错误，请重新输入！");
flag = 1;
}
}
if (month == 1)
System.out.println(year + "-" + month + "-" + day + "是这年的第" + day
+ "天");
else {
for (int i = 2; i <= month; i++) {
switch (i) {
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
days = 31;
break;
case 2:
if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0)
days = 29;
else
days = 28;
break;
case 4:
case 6:
case 9:
case 11:
days = 30;
break;
}
sum += days;
}
System.out.println(year + "-" + month + "-" + day + "是这年的第"
+ (sum + day) + "天");
}
}
}