ORACLE函数MONTHS的模拟
Java是否具有Oracle的函数MONTHS_BETWEEN某些类比？
你可以这样做：
public static int monthsBetween(Date minuend, Date subtrahend){
Calendar cal = Calendar.getInstance();
cal.setTime(minuend);
int minuendMonth = cal.get(Calendar.MONTH);
int minuendYear = cal.get(Calendar.YEAR);
cal.setTime(subtrahend);
int subtrahendMonth = cal.get(Calendar.MONTH);
int subtrahendYear = cal.get(Calendar.YEAR);
return ((minuendYear - subtrahendYear) * (cal.getMaximum(Calendar.MONTH)+1)) +
(minuendMonth - subtrahendMonth);
}
编辑：
根据这个文档MONTHS_BETWEEN返回一个小数结果，我认为这个方法也是这样做的：
public static void main(String[] args) throws ParseException {
SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yyyy");
Date d = sdf.parse("02/02/1995");
Date d2 = sdf.parse("01/01/1995");
System.out.println(monthsBetween(d, d2));
}
public static double monthsBetween(Date baseDate, Date dateToSubstract){
Calendar cal = Calendar.getInstance();
cal.setTime(baseDate);
int baseDayOfYear = cal.get(Calendar.DAY_OF_YEAR);
int baseMonth = cal.get(Calendar.MONTH);
int baseYear = cal.get(Calendar.YEAR);
cal.setTime(dateToSubstract);
int subDayOfYear = cal.get(Calendar.DAY_OF_YEAR);
int subMonth = cal.get(Calendar.MONTH);
int subYear = cal.get(Calendar.YEAR);
//int fullMonth = ((baseYear - subYear) * (cal.getMaximum(Calendar.MONTH)+1)) +
//(baseMonth - subMonth);
//System.out.println(fullMonth);
return ((baseYear - subYear) * (cal.getMaximum(Calendar.MONTH)+1)) +
(baseDayOfYear-subDayOfYear)/31.0;
}
我遇到了同样的需求，从@ alain.janinm开始回答，这很好，但在某些情况下并没有给出完全相同的结果。
例如：
考虑17/02/2013和2016年3月11日之间的几个月（ "dd/MM/yyyy" ）
Oracle结果： 36,8064516129032
来自@ Alain.janinm的Java方法回答： 36.74193548387097
以下是我所做的更改，以便更接近Oracle的months_between()函数：
public static double monthsBetween(Date startDate, Date endDate){
Calendar cal = Calendar.getInstance();
cal.setTime(startDate);
int startDayOfMonth = cal.get(Calendar.DAY_OF_MONTH);
int startMonth = cal.get(Calendar.MONTH);
int startYear = cal.get(Calendar.YEAR);
cal.setTime(endDate);
int endDayOfMonth = cal.get(Calendar.DAY_OF_MONTH);
int endMonth = cal.get(Calendar.MONTH);
int endYear = cal.get(Calendar.YEAR);
int diffMonths = endMonth - startMonth;
int diffYears = endYear - startYear;
int diffDays = endDayOfMonth - startDayOfMonth;
return (diffYears * 12) + diffMonths + diffDays/31.0;
}
通过此功能， 36.806451612903224日和36.806451612903224日的电话会议结果是： 36.806451612903224
注意：根据我的理解，Oracle的months_between()函数认为所有的月份都是31天
在Joda时间，org.joda.time.Months类中有几个月。
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