如何在格里高利历中减去两个日期？

Question

如何编写一个函数来返回Gregorian Callendar中两个日期之间的天数？我应该用什么类型转换我的日期和方式？

public int substractDate(GregorianCalendar beginningDate, GregorianCalendar endingDate){
            return dif;
        }

Answer 1

使用GregorianCalendar对象，它是Calendar的子类：

    String dayPattern = "DD";
    SimpleDateFormat days = new SimpleDateFormat(dayPattern);
    return Integer.parseInt(days.format(endingDate.getTimeInMillis()-beginningDate.getTimeInMillis()));

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