//Calendar.MONTH ，这是一个特殊于日历的值。

//在格里高利历和罗马儒略历中一年中的第一个月是 JANUARY，它为 0；最后一个月取决于一年中的月份数。

//

//所以这个值的初始值为0，所以我们用它来表示日历月份时需要加1

        var c = Calendar.getInstance();

        System.out.println(c.get(Calendar.DAY_OF_WEEK));

        System.out.println(c.get(Calendar.YEAR));

        System.out.println(c.get(Calendar.MONTH));

        System.out.println(c.get(Calendar.DATE));

        System.out.println(c.get(Calendar.HOUR));

        System.out.println(c.get(Calendar.MINUTE));

        System.out.println(c.get(Calendar.SECOND));

        c.set(,,,,,);

        System.out.println(c.get(Calendar.YEAR));

        System.out.println(c.get(Calendar.MONTH));

        System.out.println(c.get(Calendar.DATE));

        System.out.println(c.get(Calendar.HOUR));

        System.out.println(c.get(Calendar.MINUTE));

        System.out.println(c.get(Calendar.SECOND));

        // add 会进位

        c.add(Calendar.YEAR, -);

        System.out.println(c.getTime());

        // roll 当修改的字段超出它的允许范围时，上一级字段不会增大。

        c.roll(Calendar.MONTH, -);

        System.out.println(c.getTime());

6

2019

6

26

8

54

16

2003

10

23

0

32

23

Sat Nov 23 12:32:23 CST 2002

Mon Dec 23 12:32:23 CST 2002