我用的是Calendar类，若觉得我用的类不好，请告示我更好的，我会虚心接受。

请告示我如何求：(包括具体什么类，最好有代码。)
1.日期之间差值
2.时分秒的差值


谢谢！

import java.util.*;

取值你的JDK版本是多少，在JDK1.4下完全没问题

package ppmsys.pre.client;

import java.util.*;
import java.text.*;
/**
SimpleDateFormat sdf=new SimpleDateFormat("yyyyMMdd");
String str="20011230";
Date dt=sdf.parse(str,new ParsePosition(0));
Calendar rightNow = Calendar.getInstance();
rightNow.setTime(dt);
rightNow.add(Calendar.DATE,2);//你要加减的日期
Date dt1=rightNow.getTime();
String reStr=sdf.format(dt1,"",new FieldPosition(0));
System.out.println(reStr);
 *
 */

public class ThreeDaysAgo
{
public static void main(String args[])
{
GregorianCalendar calendar = new GregorianCalendar();
Date date = calendar.getTime ();
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

System.out.println ("Today: "+df.format (date));

calendar.set (Calendar.DATE,
calendar.get (Calendar.DATE)-3);
date = calendar.getTime ();
System.out.println ("Three days ago: "+df.format (date));

                 String[] ids = TimeZone.getAvailableIDs(-8 * 60 * 60 * 1000);
 // if no ids were returned, something is wrong. get out.
 if (ids.length == 0)
     System.exit(0);

  // begin output
 System.out.println("Current Time");

 // create a Pacific Standard Time time zone
 SimpleTimeZone pdt = new SimpleTimeZone(-8 * 60 * 60 * 1000, ids[0]);

 // set up rules for daylight savings time
 pdt.setStartRule(Calendar.APRIL, 1, Calendar.SUNDAY, 2 * 60 * 60 * 1000);
 pdt.setEndRule(Calendar.OCTOBER, -1, Calendar.SUNDAY, 2 * 60 * 60 * 1000);

 // create a GregorianCalendar with the Pacific Daylight time zone
 // and the current date and time
 Calendar calendar1 = new GregorianCalendar(pdt);
 Date trialTime = new Date();
 calendar1.setTime(trialTime);

 // print out a bunch of interesting things
 System.out.println("ERA: " + calendar1.get(Calendar.ERA));
 System.out.println("YEAR: " + calendar1.get(Calendar.YEAR));
 System.out.println("MONTH: " + calendar1.get(Calendar.MONTH));
 System.out.println("WEEK_OF_YEAR: " + calendar1.get(Calendar.WEEK_OF_YEAR));
 System.out.println("WEEK_OF_MONTH: " + calendar1.get(Calendar.WEEK_OF_MONTH));
 System.out.println("DATE: " + calendar1.get(Calendar.DATE));
 System.out.println("DAY_OF_MONTH: " + calendar1.get(Calendar.DAY_OF_MONTH));
 System.out.println("DAY_OF_YEAR: " + calendar1.get(Calendar.DAY_OF_YEAR));
 System.out.println("DAY_OF_WEEK: " + calendar1.get(Calendar.DAY_OF_WEEK));
 System.out.println("DAY_OF_WEEK_IN_MONTH: "+ calendar1.get(Calendar.DAY_OF_WEEK_IN_MONTH));
 System.out.println("AM_PM: " + calendar1.get(Calendar.AM_PM));
 System.out.println("HOUR: " + calendar1.get(Calendar.HOUR));
 System.out.println("HOUR_OF_DAY: " + calendar1.get(Calendar.HOUR_OF_DAY));
 System.out.println("MINUTE: " + calendar1.get(Calendar.MINUTE));
 System.out.println("SECOND: " + calendar1.get(Calendar.SECOND));
 System.out.println("MILLISECOND: " + calendar1.get(Calendar.MILLISECOND));
 System.out.println("ZONE_OFFSET: "
                    + (calendar1.get(Calendar.ZONE_OFFSET)/(60*60*1000)));
 System.out.println("DST_OFFSET: "
                    + (calendar1.get(Calendar.DST_OFFSET)/(60*60*1000)));

 System.out.println("Current Time, with hour reset to 3");
 calendar1.clear(Calendar.HOUR_OF_DAY); // so doesn't override
 calendar1.set(Calendar.HOUR, 3);
 System.out.println("ERA: " + calendar1.get(Calendar.ERA));
 System.out.println("YEAR: " + calendar1.get(Calendar.YEAR));
 System.out.println("MONTH: " + calendar1.get(Calendar.MONTH));
 System.out.println("WEEK_OF_YEAR: " + calendar1.get(Calendar.WEEK_OF_YEAR));
 System.out.println("WEEK_OF_MONTH: " + calendar1.get(Calendar.WEEK_OF_MONTH));
 System.out.println("DATE: " + calendar1.get(Calendar.DATE));
 System.out.println("DAY_OF_MONTH: " + calendar1.get(Calendar.DAY_OF_MONTH));
 System.out.println("DAY_OF_YEAR: " + calendar1.get(Calendar.DAY_OF_YEAR));
 System.out.println("DAY_OF_WEEK: " + calendar1.get(Calendar.DAY_OF_WEEK));
 System.out.println("DAY_OF_WEEK_IN_MONTH: "
                    + calendar1.get(Calendar.DAY_OF_WEEK_IN_MONTH));
 System.out.println("AM_PM: " + calendar1.get(Calendar.AM_PM));
 System.out.println("HOUR: " + calendar1.get(Calendar.HOUR));
 System.out.println("HOUR_OF_DAY: " + calendar1.get(Calendar.HOUR_OF_DAY));
 System.out.println("MINUTE: " + calendar1.get(Calendar.MINUTE));
 System.out.println("SECOND: " + calendar1.get(Calendar.SECOND));
 System.out.println("MILLISECOND: " + calendar1.get(Calendar.MILLISECOND));
 System.out.println("ZONE_OFFSET: "
        + (calendar1.get(Calendar.ZONE_OFFSET)/(60*60*1000))); // in hours
 System.out.println("DST_OFFSET: "
        + (calendar1.get(Calendar.DST_OFFSET)/(60*60*1000))); // in hours
}
}


记得给我分哦  ：）

对不起，我没有做过这样的内容，我现在主要是用javax.swing.*，做程序，惭愧！！