关于日期的惯用算法

关于日期的常用算法

 关于日期的常用算法有很多，但如果掌握了基本的算法，难一点的可以分解为简单的，各个击破。

1）判断一年是否为闰年：

//判断一年是否为闰年static boolean IsLeapYear(int year){return (year % 400 == 0 || year % 4 == 0 && year % 100 != 0);}

2）获得某一年的总天数：（闰年366天，非闰年355）

//获得某一年的总天数static int GetAllDays(int year){return (IsLeapYear(year)? 366: 365);}

3）获得某年、某月的最大天数

//获得某年、某月的最大天数static int GetMaxDay(int year,int month){switch(month){case 1:case 3:case 5:case 7:case 8:case 10:case 12:return 31;case 4:case 6:case 9:case 11:return 30;case 2:return (IsLeapYear(year)? 29: 28);default:return -1;}}

4)获得某年、某月、某日是这一年的第几天

//获得某年、某月、某日是这一年的第几天static int GetDays(int year,int month,int day){int sum = 0;for(int i = 1; i < month ; i++){sum += GetMaxDay(year,i);}return sum+day;}

5）获得某年某月的下一天

//获得某年某月某日的下一天static void GetNextDay(int year,int month,int day){if(day != GetMaxDay(year,month)){day++;}else{    if(month != 12)    {month++; day = 1;}    else    {year++; month = day =1;}}}

6）获得某年某日的前一天

//获得某年某月某日的前一天static void GetPreDay(int year,int month,int day){if(day != 1){day--;}else{if(month != 1){month--;GetMaxDay(year,month);}else{year--;month = 12;day = 31;}}}

7）获得某年某月某日n天后的日期

//获得某年某月某日n天之后的日期static void GetXDay(int year,int month,int day,int X){for(int i = 1; i<= X; i++){if(day != GetMaxDay(year,month)){day++;}else{if(month != 12){month++;day = 1;}else{year++;month = day = 1;}}}System.out.println(X+" 天后是："+year+"-"+month+"-"+day);}

8）比较日期大小

//比较日期大小static int CompareDay(int year1,int month1,int day1, int year2,int month2,int day2){return year1 != year2? (year1-year2):(month1 != month2 ? (month1-month2): day1-day2);}

9）求日期之差

//求日期之差static int GetDateDiff1(int year1,int month1,int day1,int year2,int month2,int day2){int sum = GetAllDays(year1) - GetDays(year1,month1,day1);for(int i = year1+1; i < year2; i++ ){sum += GetAllDays(i);}sum += GetDays(year2,month2,day2);return sum;}static int GetDateDiff(int year1,int month1,int day1,int year2,int month2,int day2){if(CompareDay(year1,month1,day1,year2,month2,day2) > 0){return -GetDateDiff1(year2,month2,day2,year1,month1,day1);}else if(CompareDay(year1,month1,day1,year2,month2,day2) < 0){return GetDateDiff1(year1,month1,day1,year2,month2,day2);}return 0;}