Java 中Calendar的使用

package pack.java.calendar.demo;

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
/**
 * Calendar的使用;
 * @author ZhouHaiTao
 *
 */
public class CalendarDemo {
	private static SimpleDateFormat date_format = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
	public static void main(String[] args) {
		
		//获取calendar实例;
		Calendar calendar = Calendar.getInstance();
		
		//判断calendar是不是GregorianCalendar类的实例;
		if(calendar instanceof GregorianCalendar){
			System.out.println("属于GregorianCalendar类的实例!");
		}
		
		//从calendar对象中获得date对象，当前时间;
		Date dates =  calendar.getTime();
		
		//格式化时间;
		String date_str= date_format.format(dates);
		System.out.println(date_str);
		
		//设置月份05；代表日历的月份6月，因为月份从0开始。
		calendar.set(Calendar.MONTH, 05);
		
		int months = calendar.get(Calendar.MONTH);
		System.out.println(months);  //输出05;
		
		//设置日期为2011-07-24 09：59:50
		calendar.set(2011, 06, 24, 9, 59, 50);  
		String getDate = date_format.format(calendar.getTime());
		System.out.println(getDate);   //输出2011-07-24 09:59:50;
		
		//比较日前大小;
		if(new Date().getTime() > calendar.getTimeInMillis()){
			System.out.println("当前日期在后!");
		}else{
			System.out.println("当前日期在前!");
		}
		
		//设置当前时间为:2011-07-24 11:06:00
		calendar.setTime(new Date());  
		int year   = calendar.get(Calendar.YEAR);   //获取年;
		int month  = calendar.get(Calendar.MONTH);  //获取月;
		int date   = calendar.get(Calendar.DATE);   //获取天;
		int hour   = calendar.get(Calendar.HOUR);   //获取小时;
		int minute = calendar.get(Calendar.MINUTE); //获取分钟;
		int second = calendar.get(Calendar.SECOND); //获取秒钟;
		int hour_of_day = calendar.get(Calendar.HOUR_OF_DAY);    //第几个小时，
		int day_of_month  = calendar.get(Calendar.DAY_OF_MONTH); //这天，在一个月内是第几天. 
		int day_of_week = calendar.get(Calendar.DAY_OF_WEEK);    //这天，在一周内，是第几天.
		int day_of_year = calendar.get(Calendar.DAY_OF_YEAR);    //这天，在一年内，是第几天。
		int week_of_year = calendar.get(Calendar.WEEK_OF_YEAR);  //这周，在一年内是第几周;
		int week_of_month = calendar.get(Calendar.WEEK_OF_MONTH);//这周，在这个月是第几周;以以星期为标准；
		int zone_offset = calendar.get(Calendar.ZONE_OFFSET);    //获取时区;
		int day_of_week_in_month = calendar.get(Calendar.DAY_OF_WEEK_IN_MONTH);  //某月中第几周，按这个月1号算，1号起就是第1周，8号起就是第2周。以月份天数为标准 
		int r = calendar.get(Calendar.AM_PM);
		if(r==calendar.AM){
			System.out.println("现在是上午");
		}
		
		if(r==calendar.PM){
			System.out.println("现在是下午");
		}
		System.out.println("==================================================");
 		System.out.println(year);
 		System.out.println(month);
 		System.out.println(date);
		System.out.println(hour);
		System.out.println(minute);
		System.out.println(second);
		System.out.println(hour_of_day);
		System.out.println(day_of_month);
		System.out.println(day_of_week);
		System.out.println(day_of_year);
		System.out.println(week_of_year);
		System.out.println(week_of_month);
		System.out.println(zone_offset);
		System.out.println(day_of_week_in_month);
	}
}

//获取某个月份的 天数
private int getDaysOfMonth(String starttime){
		Date dateMomth = new SimpleDateFormat("yyyy-MM").parse(starttime);
		Calendar cal=Calendar.getInstance();
		cal.setTime(dateMomth);
		return cal.getActualMaximum(Calendar.DAY_OF_MONTH);
	}