在java中查找天差异
在咨询了几个论坛之后，我最终使用下面的代码来查找天差。 但是，我发现逻辑存在问题（可能是我的看法？）。 我看到天数在11到14之间和11到15之间是相同的。 这怎么可能？
Date createdDate = new Date((2013 + 1900), (1 + 1), 11); Date expirationDate = new Date((2013 + 1900), (1 + 1), 11); for (int i = 11; i < 20; i++) { expirationDate.setDate(i); System.out.println("11 to " + i + " = " + (int) (expirationDate.getTime() - createdDate.getTime()) / (1000 * 60 * 60 * 24)); } 输出是：
11 to 11 = 0 11 to 12 = 1 11 to 13 = 2 11 to 14 = 3 11 to 15 = 3 11 to 16 = 4 11 to 17 = 5 11 to 18 = 6 11 to 19 = 7
使用Joda Time的Days#daysBetween() 。 没有更好的方法。
DateMidnight createdDate = new DateMidnight(2013, 2, 11); for (int i = 11; i < 20; i++) { DateMidnight expirationDate = new DateMidnight(2013, 2, i); int dayDifference = Days.daysBetween(createdDate, expirationDate); System.out.println("11 to " + i + " = " + dayDifference); }
不推荐使用日期（年，日，月）构造函数。 我只想使用日历方法来获得两天之间的差异：
Calendar cal1=Calendar.getInstance(); Calendar cal2=Calendar.getInstance(); cal1.setTime(createdDate); cal2.setTime(expirationDate); System.out.println(cal2.get(Calendar.DAY_OF_MONTH )-cal1.get(Calendar.DAY_OF_MONTH ) );
编辑：
Calendar cal1 = Calendar.getInstance(); cal1.set(2013, 2, 11); Calendar cal2 = Calendar.getInstance(); cal2.set(2013, 2, 11); for (int i = 11; i < 20; i++) { cal2.set(Calendar.DATE, i); System.out.println("11 to " + i + " = " + (cal2.get(Calendar.DAY_OF_MONTH) -cal1.get(Calendar.DAY_OF_MONTH))); }
OUTPUT：
11 to 11 = 0 11 to 12 = 1 11 to 13 = 2 11 to 14 = 3 11 to 15 = 4 11 to 16 = 5 11 to 17 = 6 11 to 18 = 7 11 to 19 = 8
1000 * 60 * 60 * 24是找错差的错误方法。 您可以使用JodaTime，但有一个纯java解决方案。
我们有两个初始化变量
Calendar firstDay = ...; Calendar secondDay = ...;
和
firstDay.before(lastDay)
是true 。
跑
int firstDayNo = firstDay.get(Calendar.DAY_OF_YEAR); int secondDayNo = secondDay.get(Calendar.DAY_OF_YEAR); int dayDifference, yearMultiplier; dayDifference = -firstDayNo; yearMultiplier = secondDay.get(Calendar.YEAR) - firstDay.get(Calendar.YEAR); while (yearMultiplier > 0) { dayDifference += firstDay.getActualMaximum(Calendar.DAY_OF_YEAR); firstDay.add(Calendar.YEAR, 1); yearMultiplier--; } dayDifference += secondDayNo; return dayDifference;
使用float，我看到了问题。 使用时间戳似乎不是找到2个日期之间的天差的好方法。
11至11 = 0.0
11至12 = 1.0
11至13 = 2.0
11至14 = 3.0
11至15 = 3.9583333
11至16 = 4.9583335
11至17 = 5.9583335
11至18 = 6.9583335
11至19 = 7.9583335
outlook未来，我找到了确定日期差异的最具决定性的方法
Calendar cre_calendar = new GregorianCalendar((2013), (1), 11); Calendar exp_calendar = new GregorianCalendar((2013), (1), 19); Calendar maxDays = new GregorianCalendar(((2013)), (12), 31); if (exp_calendar.get(Calendar.DAY_OF_YEAR) < cre_calendar .get(Calendar.DAY_OF_YEAR)) { System.out .println((exp_calendar.get(Calendar.DAY_OF_YEAR) + maxDays .get(Calendar.DAY_OF_YEAR)) - cre_calendar.get(Calendar.DAY_OF_YEAR)); } else { System.out.println((exp_calendar.get(Calendar.DAY_OF_YEAR)) - cre_calendar.get(Calendar.DAY_OF_YEAR)); }
至少在当前版本中，您的代码会打印出正确的结果
11 to 11 = 0 11 to 12 = 1 11 to 13 = 2 11 to 14 = 3 11 to 15 = 4 11 to 16 = 5 11 to 17 = 6 11 to 18 = 7 11 to 19 = 8
不过new Date((2013 + 1900), (1 + 1), 11); 是不正确的，实际上是5813-03-01 。 它应该是new Date((2013 - 1900), (1 - 1), 11); 请参阅Date（int year，int month，int day）API
Parameters: year - the year minus 1900. month - the month between 0-11. date - the day of the month between 1-31.