现在是2004-03-26 13：31：40 过去是：2004-01-02 11：30：24要获得两个日期差，差的形式为：XX天XX小时XX分XX秒方法一：DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");try{    Date d1 = df.parse("2004-03-26 13:31:40");    Date d2 = df.parse("2004-01-02 11:30:24");    long diff = d1.getTime() - d2.getTime();    long days = diff / (1000 * 60 * 60 * 24);}catch (Exception e){}方法二：   SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");   .Date now = df.parse("2004-03-26 13:31:40");   .Date date=df.parse("2004-01-02 11:30:24");   long l=now.getTime()-date.getTime();   long day=l/(24*60*60*1000);   long hour=(l/(60*60*1000)-day*24);   long min=((l/(60*1000))-day*24*60-hour*60);   long s=(l/100*24*60*60-hour*60*60-min*60);   System.out.println(""+day+"天"+hour+"小时"+min+"分"+s+"秒");方法三：   SimpleDateFormat dfs = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");   .Date begin=dfs.parse("2004-01-02 11:30:24");   java.util.Date end = dfs.parse("2004-03-26 13:31:40");   long between=(end.getTime()-begin.getTime())/1000;//除以1000是为了转换成秒   long day1=between/(24*3600);   long hour1=between%(24*3600)/3600;   long minute1=between%3600/60;   long second1=between%60/60;   System.out.println(""+day1+"天"+hour1+"小时"+minute1+"分"+second1+"秒");====================================================java 比较时间大小 String s1="2008-01-25 09:12:09";String s2="2008-01-29 09:12:11";java.text.DateFormat df=new java.text.SimpleDateFormat("yyyy-MM-dd HH:mm:ss");java.util.Calendar c1=java.util.Calendar.getInstance();java.util.Calendar c2=java.util.Calendar.getInstance();try{c1.setTime(df.parse(s1));c2.setTime(df.parse(s2));}catch(java.text.ParseException e){System.err.println("格式不正确");}int result=c1.compareTo(c2);if(result==0)System.out.println("c1相等c2");else if(result<0)System.out.println("c1小于c2");elseSystem.out.println("c1大于c2");