java之Calendar的一些用法

package calendar;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

/**
* java之Calendar的一些用法
*/
public class TestCalendar {

public static void main(String[] args) throws ParseException {
//Date转Calendar
String time="2011-05-12 23:59:59";
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); //HH是24小时制，hh是12小时制
Date date = sdf.parse(time);
System.out.println(sdf.format(date));
Calendar c = Calendar.getInstance();
c.setTime(date);
System.out.println(sdf.format(c.getTime()));

//日期加2天
c.add(Calendar.DAY_OF_MONTH, 2);
System.out.println(sdf.format(c.getTime()));

//日期减1天
c.add(Calendar.DATE, -1);
System.out.println(sdf.format(c.getTime()));

//年、月、日、时、分、秒
Calendar calendar = Calendar.getInstance();
int year = calendar.get(Calendar.YEAR);
int month = calendar.get(Calendar.MONTH)+1;
int day = calendar.get(Calendar.DATE);
int hour = calendar.get(Calendar.HOUR_OF_DAY);
int minute = calendar.get(Calendar.MINUTE);
int second = calendar.get(Calendar.SECOND);
System.out.println(year + "-" + month + "-" + day + " " + hour + ":" + minute + ":" + second);

//星期
sdf = new SimpleDateFormat("yyyy-MM-dd");
int i = calendar.get(Calendar.DAY_OF_WEEK) - 1; //值为0到6，分别代表星期天到星期六
System.out.println("今天星期几：" + i);
calendar.add(Calendar.DATE, -i); //上星期天
String endDate = sdf.format(calendar.getTime());
System.out.println("上星期天是：" + endDate);
calendar.add(Calendar.DATE, -6); //上星期一
String startDate = sdf.format(calendar.getTime());
System.out.println("上星期一是：" + startDate);

//取当月的第一天与最后一天
Calendar cal = Calendar.getInstance();
cal.setTime(new Date());
cal.set(Calendar.DAY_OF_MONTH, 1);
System.out.println("本月第一天：" + new SimpleDateFormat("yyyy-MM-dd").format(cal.getTime()));
cal.roll(Calendar.DAY_OF_MONTH, -1);
System.out.println("本月最后一天：" + new SimpleDateFormat("yyyy-MM-dd").format(cal.getTime()));
System.out.println("本月最后一天：" + cal.getActualMaximum(Calendar.DAY_OF_MONTH));
}

}

运行结果：

2011-05-12 23:59:59

2011-05-12 23:59:59

2011-05-14 23:59:59

2011-05-13 23:59:59

2016-5-29 21:3:4

今天星期几：0

上星期天是：2016-05-29

上星期一是：2016-05-23

本月第一天：2016-05-01

本月最后一天：2016-05-31

本月最后一天：31