Java对时间操作的一些封装函数
1. 计算两天之间相隔几天的Java函数
/** * 计算两天之间相差几天 * @param startTime * @param endTime * @return * * 取得两个时间段的时间间隔 * return t2 与t1的间隔天数 * throws ParseException 如果输入的日期格式不是0000-00-00 格式抛出异常 */ public static int betweenTwoDays(String startTime,String endTime){ String startYearStr = startTime.substring(0, 4); String endYearStr = endTime.substring(0, 4); String startMonthStr = startTime.substring(4, 6); String endMonthStr = endTime.substring(4, 6); String startDayStr = startTime.substring(6, 8); String endDayStr = endTime.substring(6, 8); String t1 = startYearStr+"-"+startMonthStr+"-"+startDayStr; String t2 = endYearStr+"-"+endMonthStr+"-"+endDayStr; DateFormat format = new SimpleDateFormat("yyyy-MM-dd"); int betweenDays = 0; Date d1 = null; Date d2 = null; try { d1 = format.parse(t1); d2 = format.parse(t2); Calendar c1 = Calendar.getInstance(); Calendar c2 = Calendar.getInstance(); c1.setTime(d1); c2.setTime(d2); int betweenYears = c2.get(Calendar.YEAR)-c1.get(Calendar.YEAR); betweenDays = c2.get(Calendar.DAY_OF_YEAR)-c1.get(Calendar.DAY_OF_YEAR); for(int i=0;i<betweenYears;i++){ c1.set(Calendar.YEAR,(c1.get(Calendar.YEAR)+1)); betweenDays += c1.getMaximum(Calendar.DAY_OF_YEAR); } } catch (ParseException e) { e.printStackTrace(); } return betweenDays; }
2. 判断是否为闰年
/*** * 判断是否为闰年 * @param yearStr * @return */ public static boolean isLoop(String yearStr){ int year = Integer.parseInt(yearStr); boolean flag = false; if ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0)){ flag = true; } return flag; } public static boolean isLoop(int year){ boolean flag = false; if ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0)){ flag = true; } return flag; }
3.判断前多少天是那一天的函数
/**** * 计算出day的before天之前是哪一天 * @param day * @return */ public static String getDayBefore(String day,int beforeDay){ String resultDay = null; String YearStr = day.substring(0, 4); String MonthStr = day.substring(4, 6); String DayStr = day.substring(6, 8); int yearInt = Integer.parseInt(YearStr); int monthInt = Integer.parseInt(MonthStr); int dayInt = Integer.parseInt(DayStr); int[] month; if(isLoop(yearInt)){ month = new int[]{0,31,29,31,30,31,30,31,31,30,31,30,31}; } else{ month = new int[]{0,31,28,31,30,31,30,31,31,30,31,30,31}; } for(int i=0;i<beforeDay;i++){ dayInt--; if(dayInt<=0){ monthInt--; if(monthInt<=0){ yearInt--; monthInt = 12; dayInt = month[monthInt]; } else{ dayInt = month[monthInt]; } } } resultDay = ""+yearInt+String.format("%02d",monthInt)+String.format("%02d",dayInt); return resultDay; }
一些转载之作：
1.计算某一月份的最大天数
Calendar time=Calendar.getInstance();
time.clear();
time.set(Calendar.YEAR,year);
time.set(Calendar.MONTH,i-1);//注意,Calendar对象默认一月为0
int day=time.getActualMaximum(Calendar.DAY_OF_MONTH);//本月份的天数
注：在使用set方法之前，必须先clear一下，否则很多信息会继承自系统当前时间
2.Calendar和Date的转化
(1) Calendar转化为Date
Calendar cal=Calendar.getInstance();
Date date=cal.getTime();
(2) Date转化为Calendar
Date date=new Date();
Calendar cal=Calendar.getInstance();
cal.setTime(date);
3.格式化输出日期时间
Date date=new Date();
SimpleDateFormat df=new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
System.out.println(df.format(date));
4.计算一年中的第几星期
(1)计算某一天是一年中的第几星期
Calendar cal=Calendar.getInstance();
cal.set(Calendar.YEAR, 2006);
cal.set(Calendar.MONTH, 8);
cal.set(Calendar.DAY_OF_MONTH, 3);
int weekno=cal.get(Calendar.WEEK_OF_YEAR);
(2)计算一年中的第几星期是几号
SimpleDateFormat df=new SimpleDateFormat("yyyy-MM-dd");
Calendar cal=Calendar.getInstance();
cal.set(Calendar.YEAR, 2006);
cal.set(Calendar.WEEK_OF_YEAR, 1);
cal.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
System.out.println(df.format(cal.getTime()));
输出:
2006-01-02
5.add()和roll()的用法
(1)add()方法
SimpleDateFormat df=new SimpleDateFormat("yyyy-MM-dd");
Calendar cal=Calendar.getInstance();
cal.set(Calendar.YEAR, 2006);
cal.set(Calendar.MONTH, 8);
cal.set(Calendar.DAY_OF_MONTH, 3);
cal.add(Calendar.DATE, -4);
Date date=cal.getTime();
System.out.println(df.format(date));
cal.add(Calendar.DATE, 4);
date=cal.getTime();
System.out.println(df.format(date));
输出：
2006-08-30
2006-09-03
(2)roll方法
cal.set(Calendar.YEAR, 2006);
cal.set(Calendar.MONTH, 8);
cal.set(Calendar.DAY_OF_MONTH, 3);
cal.roll(Calendar.DATE, -4);
date=cal.getTime();
System.out.println(df.format(date));
cal.roll(Calendar.DATE, 4);
date=cal.getTime();
System.out.println(df.format(date));
输出：
2006-09-29
2006-09-03
可见，roll()方法在本月内循环，一般使用add()方法；
6.计算两个任意时间中间的间隔天数
(1)传进Calendar对象
/**计算两个时间之间相隔天数
* @param startday 开始时间 * @param endday 结束时间 * @return
*/
public
int
getIntervalDays(Calendar startday,Calendar endday)
{ //确保startday在endday之前
if(startday.after(endday)){ Calendar cal=startday; startday=endday; endday=cal;
} //分别得到两个时间的毫秒数 long sl=startday.getTimeInMillis(); long el=endday.getTimeInMillis(); long ei=el-sl; //根据毫秒数计算间隔天数 return (int)(ei/(1000*60*60*24)); }
/**计算两个时间之间相隔天数 * @param startday 开始时间 * @param endday 结束时间 * @return */
public
int
getIntervalDays(Date startday,Date endday)
{ //确保startday在endday之前 if(startday.after(endday)){ Date cal=startday; startday=endday; endday=cal; } //分别得到两个时间的毫秒数 long sl=startday.getTime(); long el=endday.getTime(); long ei=el-sl; //根据毫秒数计算间隔天数 return (int)(ei/(1000*60*60*24)); }
注：以上方法是完全按时间计算，有时并不能令人满意，如：
startday="2006-10-11 20:00:00"
endday="2006-10-12 8:00:00"
计算结果为0，但是我们也许相让计算结果变为1，此时可以用如下方法实现：
在传参之前，先设定endday的时间，如：
endday.set(Calendar.HOUR_OF_DAY, 23);
endday.set(Calendar.MINUTE, 59);
endday.set(Calendar.SECOND, 59);
endday.set(Calendar.MILLISECOND, 59);
这样再传进去startday,endday，则结果就如我们所愿了。不过，如果嫌以上方法麻烦，可以参考以下方法：
(3)改进精确计算相隔天数的方法
public
int
getDaysBetween (Calendar d1, Calendar d2)
{ if (d1.after(d2)) { // swap dates so that d1 is start and d2 is end java.util.Calendar swap = d1; d1 = d2; d2 = swap; } int days = d2.get(Calendar.DAY_OF_YEAR) - d1.get(Calendar.DAY_OF_YEAR); int y2 = d2.get(Calendar.YEAR); if (d1.get(Calendar.YEAR) != y2) { d1 = (Calendar) d1.clone(); do { days += d1.getActualMaximum(Calendar.DAY_OF_YEAR);//得到当年的实际天数 d1.add(Calendar.YEAR, 1); } while (d1.get(Calendar.YEAR) != y2); } return days; }