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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//判断一年是否为闰年 
    static boolean IsLeapYear(int year){ 

        return (year %
400 == 0 || year %
4 == 0 && year %
100 != 0); 

    } 

//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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//获得某一年的总天数 
    static int GetAllDays(int year){ 

        return (IsLeapYear(year)?
366: 365); 

    } 

//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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//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; 

        } 
    } 

//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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//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; 

    } 

//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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//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;} 

        } 
    } 

//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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//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; 
            } 
        } 
    } 

//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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//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); 

         
         
    } 

//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); 

    } 

//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; 

    }