题目：
输入某年某月某日，判断这一天是这一年的第几天？ 1. 程序分析：以 3 月 5 日为例，应该先把前两个月的加起来， 然后再加上 5
天即本年的第几天， 特殊情况，闰年且输入月份大于 3 时需考虑多加一天。
1 public class _014JudgmentDate { 2 3 public static void main(String[] args) { 4 while (true) { 5 days(); 6 } 7 } 8 9 private static void days() { 10 int year, month, day; 11 int days = 0; 12 int feb = 28; 13 14 Scanner scanner = new Scanner(System.in); 15 System.out.println("请输入年份:"); 16 year = scanner.nextInt(); 17 System.out.println("请输入月份:"); 18 month = scanner.nextInt(); 19 System.out.println("请输入天数"); 20 day = scanner.nextInt(); 21 22 if (year < 0 || month < 0 || month > 12 || day < 0 || day > 31) { 23 System.out.println("请重新输入"); 24 } else { 25 26 for (int i = 1; i < month; i++) { 27 switch (month) { 28 case 1: 29 days = day; 30 break; 31 case 2: 32 if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0) { 33 feb = 29; 34 } else { 35 feb = 28; 36 } 37 days = 31 + day; 38 break; 39 case 3: 40 days = 31 + feb + day; 41 break; 42 case 4: 43 days = 31 + feb + 31 + day; 44 break; 45 case 5: 46 days = 31 + feb + 31 + 30 + day; 47 break; 48 case 6: 49 days = 31 + feb + 31 + 30 + 31 + day; 50 break; 51 case 7: 52 days = 31 + feb + 31 + 30 + 31 + 30 + day; 53 break; 54 case 8: 55 days = 31 + feb + 31 + 30 + 31 + 30 + 31 + day; 56 break; 57 case 9: 58 days = 31 + feb + 31 + 30 + 31 + 30 + 31 + 31 + day; 59 break; 60 case 10: 61 days = 31 + feb + 31 + 30 + 31 + 30 + 31 + 31 + 30 + day; 62 break; 63 case 11: 64 days = 31 + feb + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 65 + day; 66 break; 67 case 12: 68 days = 31 + feb + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 69 + 30 + day; 70 } 71 System.out.println(year + " 年 " + month + " 月 " + day 72 + "号是今年的第" + days + "天"); 73 } 74 } 75 } 76 77 }