Calendar类实现日期的偏移

Calendar类：

add()方法实现时间的偏移

set()方法设置时间

import java.util.Calendar;

public class CalendarDemo {

public static void main(String[] args) {

/*
* 演示日历
* Calendar
*/

Calendar c = Calendar.getInstance();//c里面维护了一个map集合，键值

//对日历对象进行其中日期的定义
// c.set(Calendar.YEAR, 2012);
// c.set(2013,13,6);

//日期的偏移
// c.add(Calendar.MONTH, 4);

//任意给你一年，问：这一年的二月有多少天
// int year = 2010;
// c.set(year, 2,1);
// c.add(Calendar.DAY_OF_MONTH, -1);

//面试题：获取昨天的这个时刻
c.add(Calendar.DAY_OF_MONTH, -1);

showCalendar(c);

}

private static void showCalendar(Calendar c) {
int year = c.get(Calendar.YEAR);
int month = c.get(Calendar.MONTH)+1;//月份在计算机中表示的是从0-11月
int day = c.get(Calendar.DAY_OF_MONTH);
int hour = c.get(Calendar.HOUR);
int minute = c.get(Calendar.MINUTE);
int second = c.get(Calendar.SECOND);
String week = getWeek(c.get(Calendar.DAY_OF_WEEK));//星期日为一周的第一天

System.out.println(year+"年"+month+"月"+day+"日"+week+hour+"时"+minute+"分"+second+"秒");
}

private static String getWeek(int i) {
if(i<=0||i>7)
throw new RuntimeException(i+"错误的星期");
String [] s = {"","星期日","星期一","星期二","星期三","星期四","星期五","星期六"};

return s[i];
}

}