时间简码-java

java里的时间类是比较简单的，如果没有对时间相关类总结学习过，有些需求或许不能立即写出来。现做几个简单的时间编码方法，供以后参考查阅。

 1 //获取距离当天前三个月的日期
 2 {
 3     Calendar calendar = Calendar.getInstance();
 4     calendar.add(Calendar.MONTH, -3);
 5     SimpleDateFormat format = new SimpleDateFormat("yyyyMMdd");        
 6     String predate = format.format(calendar.getTime());
 7     Date now = new Date();
 8     SimpleDateFormat nformat = new SimpleDateFormat("yyyyMMdd");
 9     String nowdate = nformat.format(now);
10     System.out.println(predate+";"+nowdate);
11 }

输出：
20130826;20131126

1 //日期date是星期几
2 int getWeekNum(Date date){
3     Calendar calendar = Calendar.getInstance();
4     calendar.setTime(date);
5     int num = calendar.get(Calendar.DAY_OF_WEEK);
6     return num==1?7:num-1;
7 }

输出：
星期一：1
星期二：2
星期三：3
星期四：4
星期五：5
星期六：6
星期日：7

  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 }
  5 //获得某一年的总天数
  6 static int GetAllDays(int year){
  7     return (IsLeapYear(year)? 366: 365);
  8 }
  9 //获得某年、某月的最大天数
 10 static int GetMaxDay(int year,int month){
 11     switch(month)
 12     {
 13     case 1:
 14     case 3:
 15     case 5:
 16     case 7:
 17     case 8:
 18     case 10:
 19     case 12:
 20                 return 31;        
 21     case 4:
 22     case 6:
 23     case 9:
 24     case 11:
 25         return 30;    
 26     case 2:
 27         return (IsLeapYear(year)? 29: 28);    
 28     default:
 29         return -1;
 30     }
 31 }
 32 //获得某年、某月、某日是这一年的第几天
 33 static int GetDays(int year,int month,int day){
 34     int sum = 0;
 35     
 36     for(int i = 1; i < month ; i++){
 37         sum += GetMaxDay(year,i);
 38     }
 39     
 40     return sum+day;
 41 }
 42 //获得某年某月某日的下一天
 43 static void GetNextDay(int year,int month,int day){
 44     if(day != GetMaxDay(year,month)){
 45         day++;
 46     }else
 47     {
 48         if(month != 12)
 49         {month++; day = 1;}
 50         else
 51         {year++; month = day =1;}
 52     }
 53 }
 54 //获得某年某月某日的前一天
 55 static void GetPreDay(int year,int month,int day){
 56     if(day != 1){
 57         day--;
 58     }else{
 59         if(month != 1){
 60             month--;
 61             GetMaxDay(year,month);
 62         }
 63         else{
 64             year--;month = 12;day = 31;
 65         }
 66     }
 67 }
 68 //获得某年某月某日n天之后的日期
 69 static void GetXDay(int year,int month,int day,int X){
 70     for(int i = 1; i<= X; i++){
 71         if(day != GetMaxDay(year,month)){
 72             day++;
 73         }else{
 74             if(month != 12){
 75                 month++;day = 1;
 76             }else{
 77                 year++;
 78                 month = day = 1;
 79             }
 80         }
 81     }
 82     System.out.println(X+" 天后是："+year+"-"+month+"-"+day);
 83     
 84         
 85 }
 86 //比较日期大小
 87 static int CompareDay(int year1,int month1,int day1, int year2,int month2,int day2){
 88     return year1 != year2? (year1-year2):(month1 != month2 ? (month1-month2): day1-day2);
 89 }
 90 //求日期之差
 91 static int GetDateDiff1(int year1,int month1,int day1,int year2,int month2,int day2){
 92     int sum = GetAllDays(year1) - GetDays(year1,month1,day1);
 93     for(int i = year1+1; i < year2; i++ ){
 94         sum += GetAllDays(i);
 95     }
 96     sum += GetDays(year2,month2,day2);
 97     return sum;
 98 }
 99 static int GetDateDiff(int year1,int month1,int day1,int year2,int month2,int day2){
100         if(CompareDay(year1,month1,day1,year2,month2,day2) > 0){
101         return -GetDateDiff1(year2,month2,day2,year1,month1,day1);
102     }else if(CompareDay(year1,month1,day1,year2,month2,day2) < 0){
103         return GetDateDiff1(year1,month1,day1,year2,month2,day2);
104     }
105     return 0;
106 }

 1 //指定时间距离当前时间
 2 String getAwayTime(long time){
 3     Calendar calendar = Calendar.getInstance();
 4     long awaytime = calendar.getTimeInMillis()-time;
 5     if(awaytime/1000 < 60){
 6         return "不到1分钟!";
 7     }
 8     if(awaytime/1000/60 < 60){
 9         return awaytime/1000/60+"分钟前！";
10     }
11     if(awaytime/1000/60/60 < 24){
12         return awaytime/1000/60/60+"小时前！";
13     }
14     return awaytime/1000/60/60/24+"天前！";
15 }

    /**
     * 获取当前日期 
     * 如 20120412
     * 
     */
    public static String getCurrDate(){
        SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");
        return sdf.format(new Date());
    }
    /**
     * 获取当前年份 
     * 如 2012
     * 
     */
    public static String getCurrDate(){
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy");
        return sdf.format(new Date());
    }