Why calendar.getActualMaximum(Calendar.DAY_OF_MONTH) return 31 instead of 30?

Question

Why I'm getting 31 instead of 3? Now December, so previous of Nov = 30.

Calendar calendarPreviousMonth = Calendar.getInstance();
        calendarPreviousMonth.add(Calendar.MONTH, calendarCurrent.get(Calendar.MONTH) - 1);
        System.out.println("Amount of days in month " + calendarPreviousMonth.getActualMaximum(Calendar.DAY_OF_MONTH));

Thank you!

Answer 1

查找上个月的代码应如下：

calendarPreviousMonth.add(Calendar.MONTH, -1);

Answer 2

This is wrong:

calendarPreviousMonth.add(Calendar.MONTH, calendarCurrent.get(Calendar.MONTH)-1)

You either want to add -1 to month or set it to calendarCurrent.get(Calendar.MONTH) - 1 . Not both! Try this:

calendarPreviousMonth.add(Calendar.MONTH, -1);

or this:

calendarPreviousMonth.set(Calendar.MONTH, calendarCurrent.get(Calendar.MONTH)-1)