java 时间比较 算时间差 时间格式转换【转】
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");        java.util.Date now = df.parse("2004-03-26 13:31:40");        java.util.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/1000-day*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");        java.util.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");   

方法四,

 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");    else   System.out.println("c1大于c2");   

附,时间格式转换

FastDateFormat df = FastDateFormat.getInstance("yyyy-MM-dd HH:mm:ss");    String date = df.format(java.util.Date());     

文章出处:http://hi.baidu.com/czjjzhao/blog/item/a9cc55017272d8d8267fb5bd.html