JAVA 计算时间差

比如：现在是2004-03-26 13：31：40 
       过去是：2004-01-02 11：30：24 
我现在要获得两个日期差，差的形式为：XX天XX小时XX分XX秒 
方法一：

 1 DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
 2 try
 3 {
 4     Date d1 = df.parse("2004-03-26 13:31:40");
 5     Date d2 = df.parse("2004-01-02 11:30:24");
 6     long diff = d1.getTime() - d2.getTime();
 7     long days = diff / (1000 * 60 * 60 * 24);
 8 }
 9 catch (Exception e)
10 {
11 } 

方法二：

1 SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
2    java.util.Date now = df.parse("2004-03-26 13:31:40");
3    java.util.Date date=df.parse("2004-01-02 11:30:24");
4    long l=now.getTime()-date.getTime();
5    long day=l/(24*60*60*1000);
6    long hour=(l/(60*60*1000)-day*24);
7    long min=((l/(60*1000))-day*24*60-hour*60);
8    long s=(l/1000-day*24*60*60-hour*60*60-min*60);
9    System.out.println(""+day+"天"+hour+"小时"+min+"分"+s+"秒")；

方法三：

1 SimpleDateFormat dfs = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
2    java.util.Date begin=dfs.parse("2004-01-02 11:30:24");
3    java.util.Date end = dfs.parse("2004-03-26 13:31:40");
4    long between=(end.getTime()-begin.getTime())/1000;//除以1000是为了转换成秒
5    long day1=between/(24*3600);
6    long hour1=between%(24*3600)/3600;
7    long minute1=between%3600/60;
8    long second1=between%60/60;
9    System.out.println(""+day1+"天"+hour1+"小时"+minute1+"分"+second1+"秒");

比较时间：

 1 String s1="2008-01-25 09:12:09";
 2 String s2="2008-01-29 09:12:11";
 3 java.text.DateFormat df=new java.text.SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
 4 java.util.Calendar c1=java.util.Calendar.getInstance();
 5 java.util.Calendar c2=java.util.Calendar.getInstance();
 6 try
 7 {
 8 c1.setTime(df.parse(s1));
 9 c2.setTime(df.parse(s2));
10 }catch(java.text.ParseException e){
11 System.err.println("格式不正确");
12 }
13 int result=c1.compareTo(c2);
14 if(result==0)
15 System.out.println("c1相等c2");
16 else if(result<0)
17 System.out.println("c1小于c2");
18 else
19 System.out.println("c1大于c2");