java Candar 日期使用

package pack.java.calendar.demo;  

import java.text.SimpleDateFormat;  
import java.util.Calendar;  
import java.util.Date;  
import java.util.GregorianCalendar;  
 
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);  
    }  
} 


//Java获取当前日期的前一个月，前一天的时间
Calendar calendar = Calendar.getInstance();
calendar.add(Calendar.DATE, -1);    //得到前一天
calendar.add(Calendar.MONTH, -1);    //得到前一个月
int year = calendar.get(Calendar.YEAR);
int month = calendar.get(Calendar.MONTH)+1; //注意月份加一
 
// 判断当前日期是星期几<br> 
// @param pTime 修要判断的时间<br> 
//@return dayForWeek 判断结果<br> 
// @Exception 发生异常<br>   
public static int dayForWeek(String pTime) throws Exception { 
   format = new SimpleDateFormat("yyyy-MM-dd"); 
   Calendar c = Calendar.getInstance(); 
   c.setTime(format.parse(pTime)); 
   int dayForWeek = 0; 
   if(c.get(Calendar.DAY_OF_WEEK) == 1){ 
     dayForWeek = 7; 
   }else{ 
     dayForWeek = c.get(Calendar.DAY_OF_WEEK) - 1; 
   } 
   return dayForWeek; 
}