java日期操作

package com.basic;
import java.util.*;
import java.text.*;
public class DateT {
	
	public void simpleDate(){
		//Calendar.getInstance().getTime();返回date对象
		System.out.println(new Date());
		System.out.println(new java.sql.Date(new Date().getTime()));//依照本地数据库
		System.out.println(new Date().toLocaleString());//依照本地操作系统
	}
	//日期格式化[用于程序处理]
	public String dateFormate(Date date){
		SimpleDateFormat sf=new SimpleDateFormat("yyyy-MM-dd HH-mm-ss SSS");//精确到毫秒[大小写敏感]
		String	strDate=sf.format(date);	
		return strDate;
	}
	//设置具体的时间[缺省项会按当前时间设置],定时器的应用
	public Date getSpecificDate(){
		  Calendar calendar = Calendar.getInstance();
		  calendar.set(Calendar.YEAR, 2010);//
		  calendar.set(Calendar.MONTH, 11);//0开始计数，加1
		  calendar.set(Calendar.DAY_OF_MONTH, 32);//Calendar.DATE与之同义
		  calendar.set(Calendar.HOUR_OF_DAY, 19);//指示一天中的小时,Calendar.HOUR 指示上午或下午的小时
	      calendar.set(Calendar.MINUTE, 16);//
	      calendar.set(Calendar.SECOND, 0);//
	      calendar.set(Calendar.MILLISECOND ,224);//毫秒
	      //calendar.set(2010,0,6,13,56,20);//注意月要加1
	      Date time = calendar.getTime();
	      return time;
	
	}
	//显示当前时间[可以得到星期]
	public String showCurrentDate(){
		 String[] weekdays={"","日","一","二","三","四","五","六"};
		    GregorianCalendar currentDay = new GregorianCalendar();
		    int year= currentDay.get(Calendar.YEAR);
		    int month=currentDay.get(Calendar.MONTH);
		    int today=currentDay.get(Calendar.DAY_OF_MONTH);
		    int weekday=currentDay.get(Calendar.DAY_OF_WEEK);//1~7,星期第一天星期日
		    int hour=currentDay.get(Calendar.HOUR_OF_DAY);
		    int minute=currentDay.get(Calendar.MINUTE);
		    int second=currentDay.get(Calendar.SECOND);
		    String hourS=(hour>9)?String.valueOf(hour):"0"+hour;
		    String minuteS=(minute>9)?String.valueOf(minute):"0"+minute;
		    String secondS=(second>9)?String.valueOf(second):"0"+second;
		    String now=year+"年"+(month+1)+"月"+today+"日"+" 星期"+weekdays[weekday]+" "+hourS+":"+minuteS+":"+secondS;
		    return now;
		
	}
	//日期累加,减
	public void dateAdd(){
		  Calendar c = Calendar.getInstance();
		  //c.add(Calendar.MONTH, 6);半年后的日期
		  c.add(Calendar.DATE, 183);//和DAY_OF_MONTH 是同义词
		  String date=dateFormate(c.getTime());
		  System.out.println(date);
	}
	//将字符串转为日期
	public Date strParseDate(String dstr) throws ParseException{
		DateFormat df= new SimpleDateFormat("yyyy-MM-dd");
		Date date=df.parse(dstr);
		return date;
		//-------------------------
		 //java.sql.Date date = java.sql.Date.valueOf(dstr); dstr只为yyyy-mm-dd形式
		
	}
	//日期比较[从数据库取出时间串与当前串比较]
	public void dateCompara() throws ParseException{
		String end_date = "2009-12-08";
		DateFormat df= DateFormat.getDateInstance();  
		//String dateNowStr=df.format(new Date()) ;
		//Date nowDate = df.parse(dateNowStr);
		Date endDate = df.parse(end_date);
		System.out.println(new Date().after(endDate));//不够精确
		//----------------------------
		Calendar cdb = Calendar.getInstance();
		DateFormat dft= new SimpleDateFormat("yyyy-MM-dd");
		Date dbDate=dft.parse(end_date);
		cdb.setTime(dbDate);
		Calendar cnow = Calendar.getInstance();//当前系统时间
		long i=cnow.getTimeInMillis()-cdb.getTimeInMillis();
		System.out.println(i);
		//----------------------------
		long day=cnow.getTime().getTime()-dbDate.getTime();//结果和前相同
		int days=(int)(day/24/3600/1000);
		System.out.println(days);
		
	}
    public static void main(String[] args) throws ParseException {
    	DateT d=new DateT();
    	d.simpleDate();
    	System.out.println("--------------");
    	System.out.println(d.dateFormate(new Date()));
    	System.out.println("--------------");
    	System.out.println(d.dateFormate(d.getSpecificDate()));
    	System.out.println("--------------");
    	System.out.println(d.showCurrentDate());
    	System.out.println("--------------");
    	d.dateAdd();
    	System.out.println("--------------");
    	System.out.println(d.strParseDate("2009-08-17"));
    	System.out.println("--------------");
    	d.dateCompara() ;
	}
}