jsp中的日期问题及其它[教程][简]

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 jsp中的日期问题及其它[教程][简]

jsp中的日期问题及其它:D :D :D

/**
* @author imagebear
*/

日期问题
1、获取服务器端当前日期：

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

2、获取当前年、月、日：

<%@ 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

<%@ 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

<%@ 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

<%@ 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

<%@ 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

<%@ 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

<%@ 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

<%@ 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

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

输出结果为：
33,665,448,856.66