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：

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

//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）

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1. //获得某一年的总天数 
2.     static int GetAllDays(int year){ 
3.         return (IsLeapYear(year)?366: 365); 
4.     } 

//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

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1. //获得某年、某月的最大天数 
2.     static int GetMaxDay(int year,int month){ 
3.         switch(month) 
4.         { 
5.         case 1: 
6.         case 3: 
7.         case 5: 
8.         case 7: 
9.         case 8: 
10.         case 10: 
11.         case 12: 
12.             return 31;       
13.         case 4: 
14.         case 6: 
15.         case 9: 
16.         case 11: 
17.             return 30;   
18.         case 2: 
19.             return (IsLeapYear(year)?29: 28);   
20.         default: 
21.             return -1; 
22.         } 
23.     } 

//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

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1. //获得某年、某月、某日是这一年的第几天 
2.     static int GetDays(int year,int month,int day){ 
3.         int sum = 0; 
4.          
5.         for(int i =1; i < month ; i++){ 
6.             sum += GetMaxDay(year,i); 
7.         } 
8.          
9.         return sum+day; 
10.     } 

//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

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1. //获得某年某月某日的下一天 
2.     static void GetNextDay(int year,int month,int day){ 
3.         if(day != GetMaxDay(year,month)){ 
4.             day++; 
5.         }else 
6.         { 
7.             if(month != 12) 
8.             {month++; day = 1;} 
9.             else 
10.             {year++; month = day =1;} 
11.         } 
12.     } 

//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

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1. //获得某年某月某日的前一天 
2.     static void GetPreDay(int year,int month,int day){ 
3.         if(day != 1){ 
4.             day--; 
5.         }else{ 
6.             if(month != 1){ 
7.                 month--; 
8.                 GetMaxDay(year,month); 
9.             } 
10.             else{ 
11.                 year--;month = 12;day =31; 
12.             } 
13.         } 
14.     } 

//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

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1. //获得某年某月某日n天之后的日期 
2.     static void GetXDay(int year,int month,int day,int X){ 
3.         for(int i =1; i<= X; i++){ 
4.             if(day != GetMaxDay(year,month)){ 
5.                 day++; 
6.             }else{ 
7.                 if(month !=12){ 
8.                     month++;day = 1; 
9.                 }else{ 
10.                     year++; 
11.                     month = day = 1; 
12.                 } 
13.             } 
14.         } 
15.         System.out.println(X+" 天后是："+year+"-"+month+"-"+day); 
16.          
17.          
18.     } 

//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

 

1. //比较日期大小 
2.     static int CompareDay(int year1,int month1,int day1, int year2,int month2,int day2){ 
3.         return year1 != year2? (year1-year2):(month1 != month2 ? (month1-month2): day1-day2); 
4.     } 

//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

 

1. //求日期之差 
2.     static int GetDateDiff1(int year1,int month1,int day1,int year2,int month2,int day2){ 
3.         int sum = GetAllDays(year1) - GetDays(year1,month1,day1); 
4.         for(int i = year1+1; i < year2; i++ ){ 
5.             sum += GetAllDays(i); 
6.         } 
7.         sum += GetDays(year2,month2,day2); 
8.         return sum; 
9.     } 
10.     static int GetDateDiff(int year1,int month1,int day1,int year2,int month2,int day2){ 
11.         if(CompareDay(year1,month1,day1,year2,month2,day2) >0){ 
12.             return -GetDateDiff1(year2,month2,day2,year1,month1,day1); 
13.         }else if(CompareDay(year1,month1,day1,year2,month2,day2) <0){ 
14.             return GetDateDiff1(year1,month1,day1,year2,month2,day2); 
15.         } 
16.         return 0; 
17.     }