jsp中的日期問題及其它

日期問題
1、擷取伺服器端當前日期：

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CODE:

<%@ page import="java.util.Date"%>
<%
     Date myDate = new Date();
%>

2、擷取當前年、月、日：

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CODE:

<%@ page import="java.util.Date"%>
<%
     Date myDate = new Date();
     int thisYear = myDate.getYear() + 1900;//thisYear = 2003
     int thisMonth = myDate.getMonth() + 1;//thisMonth = 5
     int thisDate = myDate.getDate();//thisDate = 30
%>

3、按本地時區輸出當前日期

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CODE:

<%@ page import="java.util.Date"%>
<%
     Date myDate = new Date();
     out.println(myDate.toLocaleString());
%>

輸出結果為：
2003-5-30
4、擷取資料庫中欄位名為”publish_time“、類型為Datetime的值

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CODE:

<%@ page import="java.util.Date"%>
<%
     ...串連資料庫...
     ResultSet rs = ...
     Date sDate = rs.getDate("publish_time");
%>
[code]
5、按照指定格式列印日期
[code]
<%@ page import="java.util.Date"%>
<%@ page import="java.text.DateFormat"%>
<%
     Date dNow = new Date();
     SimpleDateFormat formatter = new SimpleDateFormat("E yyyy.MM.dd 'at' hh:mm:ss a zzz");
     out.println("It is " + formatter.format(dNow));
%>

輸出的結果為：
It is 星期五 2003.05.30 at 11:30:46 上午 CST
(更為詳盡的格式符號請參看SimpleDateFormat類)
6、將字串轉換為日期

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CODE:

<%@ page import="java.util.Date"%>
<%@ page import="java.text.DateFormat"%>
<%
     String input = "1222-11-11";
     SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
     Date t = null;
     try{
         t = formatter.parse(input);
         out.println(t);
     }catch(ParseException e){
         out.println("unparseable using " + formatter);
     }
%>

輸出結果為：
Fri Nov 11 00:00:00 CST 1222
7、計算日期之間的間隔

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CODE:

<%@ page import="java.util.Date"%>
<%@ page import="java.text.DateFormat"%>
<%
     String input = "2003-05-01";
     SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
     Date d1 = null;
     try{
         d1 = formatter.parse(input);
     }catch(ParseException e){
         out.println("unparseable using " + formatter);
     }
    
     Date d2 = new Date();
    
     long diff = d2.getTime() - d1.getTime();
     out.println("Difference is " + (diff/(1000*60*60*24)) + " days.");
%>

輸出結果為：
Difference is 29 days.
8、日期的加減運算
方法：用Calendar類的add()方法

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CODE:

<%@ page import="java.util.*"%>
<%@ page import="java.text.*"%>
<%
     Calendar now = Calendar.getInstance();
     SimpleDateFormat formatter = new SimpleDateFormat("E yyyy.MM.dd 'at' hh:mm:ss a zzz");
     out.println("It is now " + formatter.format(now.getTime()));
     now.add(Calendar.DAY_OF_YEAR,-(365*2));
     out.println("<br>");
     out.println("Two years ago was " + formatter.format(now.getTime()));
%>

輸出結果為：
It is now 星期五 2003.05.30 at 01:45:32 下午 CST
Two years ago was 星期三 2001.05.30 at 01:45:32 下午 CST
9、比較日期
方法：用equals()、before()、after()方法

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CODE:

<%@ page import="java.util.*"%>
<%@ page import="java.text.*"%>
<%
     DateFormat df = new SimpleDateFormat("yyy-MM-dd");
     Date d1 = df.parse("2000-01-01");
     Date d2 = df.parse("1999-12-31");
    
     String relation = null;
     if(d1.equals(d2))
         relation = "the same date as";
     else if(d1.before(d2))
         relation = "before";
     else
         relation = "after";
     out.println(d1 +" is " + relation + ' ' + d2);
%>

輸出結果為：
Sat Jan 01 00:00:00 CST 2000 is after Fri Dec 31 00:00:00 CST 1999
10、記錄一件事所花費的時間
方法：調用兩次System.getTimeMillis()方法，求差值

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CODE:

<%@ page import="java.text.*"%>
<%
     long t0,t1;
     t0 = System.currentTimeMillis();
     out.println("Cyc starts at " + t0);
     int k = 0;
     for(int i =0;i<100000;i++){
         k += i;
     }
     t1 = System.currentTimeMillis();
     out.println("<br>");
     out.println("Cyc ends at " + t1);
     out.println("<br>");
     out.println("This run took " + (t1-t0) + "ms.");
%>

輸出結果為：
Cyc starts at 1054275312432
Cyc ends at 1054275312442
This run took 10ms.

其它：如何格式化小數

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CODE:

<%@ page import="java.text.*"%>
<%
     DecimalFormat df = new DecimalFormat(",###.00");
     double aNumber = 33665448856.6568975;
     String result = df.format(aNumber);
     out.println(result);
%>

輸出結果為：
33,665,448,856.66