【学习总结】Java中 Calendar 类的使用

一、getInstance 获得日历

Calendar c = Calendar.getInstance();

(1) 年_月_日_时_分_秒 常用的6个值

• Calendar.YEAR
• Calendar.MONTH
• Calendar.DAY_OF_MONTH
• Calendar.HOUR_OF_DAY
• Calendar.MINUTE
• Calendar.SECOND

System.out.println("年:" + cal.get(Calendar.YEAR));
System.out.println("月:" + (cal.get(Calendar.MONTH) + 1));       
System.out.println("日:" + cal.get(Calendar.DAY_OF_MONTH));
System.out.println("时:" + cal.get(Calendar.HOUR_OF_DAY));
System.out.println("分:" + cal.get(Calendar.MINUTE));
System.out.println("秒:" + cal.get(Calendar.SECOND));

注意：月份下标从0开始，所以取月份要 +1才能对应平时的叫法。比如当Calendar.MONTH == 11时，对应平常的12月。

(2) 设置时间（初始化）

1. 一次性初始化

Calendar cal = Calendar.getInstance();
//cal.set(year, month, date, hourOfDay, minute, second);
cal.set(2019, 0, 14, 23, 59, 59);

• 由于月份下标从0开始赋值月份要-1。

2. set 方法逐个赋值

cal.set(Calendar.YEAR, 2019);
cal.set(Calendar.MONTH, Calendar.FEBRUARY);
cal.set(Calendar.DAY_OF_MONTH, 14);
cal.set(Calendar.HOUR_OF_DAY, 23);
cal.set(Calendar.MINUTE, 59);
cal.set(Calendar.SECOND, 59);
System.out.println(cal.getTime());

• Thu Jan 14 23:59:59 CST 2019

(3) 日期运算

秒运算

Calendar cal = Calendar.getInstance();
System.out.println(cal.getTime());
cal.set(2019, 0, 14, 23, 59, 59);
cal.add(Calendar.SECOND, 1);
System.out.println(cal.getTime());

• Thu Jan 14 23:59:59 CST 2019
• Fri Jan 15 00:00:00 CST 2019

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