jsp中的日期问题及其它

/**
*       @author       imagebear
*/

日期问题
1、获取服务器端当前日期：

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代码:

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

2、获取当前年、月、日：

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代码:

<%@ 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、按本地时区输出当前日期

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代码:

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

输出结果为：
2003-5-30
4、获取数据库中字段名为”publish_time“、类型为Datetime的值

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代码:

<%@ page import="java.util.Date"%>
<%
    ...连接数据库...
    ResultSet rs = ...
    Date sDate = rs.getDate("publish_time");
%>
[code]
5、按照指定格式打印日期
[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));
%>

输出的结果为：
It is 星期五 2003.05.30 at 11:30:46 上午 CST
(更为详尽的格式符号请参看SimpleDateFormat类)
6、将字符串转换为日期

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代码:

<%@ 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);
    }
%>

输出结果为：
Fri Nov 11 00:00:00 CST 1222
7、计算日期之间的间隔

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代码:

<%@ 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.");
%>

输出结果为：
Difference is 29 days.
8、日期的加减运算
方法：用Calendar类的add()方法

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代码:

<%@ 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()));
%>

输出结果为：
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、比较日期
方法：用equals()、before()、after()方法

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代码:

<%@ 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);
%>

输出结果为：
Sat Jan 01 00:00:00 CST 2000 is after Fri Dec 31 00:00:00 CST 1999
10、记录一件事所花费的时间
方法：调用两次System.getTimeMillis()方法，求差值

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代码:

<%@ 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.");
%>

输出结果为：
Cyc starts at 1054275312432
Cyc ends at 1054275312442
This run took 10ms.

其它：如何格式化小数

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代码:

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