常用日期問題集錦
1、獲取服務器端當前日期：
<%@ page import="java.util.Date"%>
<%
Date myDate = new Date();
%>
2、獲取當前年、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、按本地時區輸出當前日期
<%@ page import="java.util.Date"%>
<%
Date myDate = new Date();
out.println(myDate.toLocaleString());
%>
輸出結果爲：
2003-5-30
4、獲取數據庫中字段名爲”publish_time“、類型爲Datetime的值
<%@ page import="java.util.Date"%>
<%
...連接數據庫...
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));
%>
輸出的結果爲：
It is 星期五 2003.05.30 at 11:30:46 上午 CST
(更爲詳盡的格式符號請參看SimpleDateFormat類)
6、將字符串轉換爲日期
<%@ 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);
}
%>
輸出結果爲：
Fri Nov 11 00:00:00 CST 1222
7、計算日期之間的間隔
<%@ 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.");
%>
輸出結果爲：
Difference is 29 days.
8、日期的加減運算
方法：用Calendar類的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()));
%>
輸出結果爲：
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
<%@ 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);
%>
輸出結果爲：
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
<%@ 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.");
%>
輸出結果爲：
Cyc starts at 1054275312432
Cyc ends at 1054275312442
This run took 10ms.
其它：如何格式化小數
<%@ page import="java.text.*"%>
<%
DecimalFormat df = new DecimalFormat(",###.00");
double aNumber = 33665448856.6568975;
String result = df.format(aNumber);
out.println(result);
%>
輸出結果爲：
33,665,448,856.66
======================
日期比較：
在JAVA中日期的計算與比較可以使用Date和DateFormat來解決，下面是一段示例代碼：
import java.text.*;
import java.util.*;
public class Test{
public static void main(String[] args){
try{
Date date=new Date();
DateFormat df=DateFormat.getDateTimeInstance();
String now=df.format(date);
System.out.println("現在時間:"+now);
System.out.println("現在時間是否在16:00之前:"+date.before(df.parse("2004-12-24 16:00:00")));
}
catch(ParseException e){System.out.print(e.getMessage());
}
}
}
***************************************************** 有是一段例子 *****************************************************
小例1:
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
public class Text {
public static void main(String[] args){
SimpleDateFormat dd=new SimpleDateFormat("yyyy-MM-dd");
String d=dd.format(new Date());
System.out.print(d);
try {
Date date=dd.parse("2007-12-12");
System.out.println(date);
} catch (ParseException e) {
e.printStackTrace();
}
}
}
下面是把Int整數轉換成Date
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
public class Text {
public static void main(String[] args){
SimpleDateFormat dd=new SimpleDateFormat("yyyyMMdd");
String d=dd.format(new Date());
System.out.print(d);
int ddd=20071212;
try {
Date date=dd.parse(ddd);
System.out.println(date);
} catch (ParseException e) {
e.printStackTrace();
}
}
}
----------------------------------------------------------------
小例2:
如何獲取當前時間？
String now=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(Calendar.getInstance().getTime());
Date createDate=convertDate(now); //轉換成Date型
//將字符串轉換成日期型的方法；
public Date convertDate(String planedDate){
Date date=new Date();
SimpleDateFormat dd=new SimpleDateFormat("yyyy-MM-dd");
String d=dd.format(new Date());
System.out.print(d);
try {
date=dd.parse(planedDate);
System.out.println(date);
} catch (ParseException e) {
e.printStackTrace();
return null;
}
return date;
}
----------------------------------------------------------------
小例3:
如何獲得系統的year,month,day？
Calendar c = Calendar.getInstance();
c.setTime(new java.util.Date());
int year = c.get(Calendar.YEAR);
int month = c.get(Calendar.MONTH)+1;
int day = c.get(Calendar.DAY_OF_MONTH);
int hour = c.get(Calendar.HOUR_OF_DAY);
int minute = c.get(Calendar.MINUTE);
int second = c.get(Calendar.SECOND);
----------------------------------------------------------------
小例4:
JAVA中獲得本地系統時間的方法
import java.util.*;
public class D
{
public static void main(String []abc)
{
int y,m,d,h,mi,s;
Calendar cal=Calendar.getInstance();
y=cal.get(Calendar.YEAR);
m=cal.get(Calendar.MONTH);
d=cal.get(Calendar.DATE);
h=cal.get(Calendar.HOUR_OF_DAY);
mi=cal.get(Calendar.MINUTE);
s=cal.get(Calendar.SECOND);
System.out.println("現在時刻是"+y+"年"+m+"月"+d+"日"+h+"時"+mi+"分"+s+"秒");
}
}
###########################################################
public class Main{
public static void main(String[] args)
{
java.util.Calendar c=java.util.Calendar.getInstance();
java.text.SimpleDateFormat f=new java.text.SimpleDateFormat("yyyy年MM月dd日hh時mm分ss秒");
System.out.println(f.format(c.getTime()));
}
}
----------------------------------------------------------------
小例5:
1>先導入兩個類java.util.*; java.text.*;
2>加簡單的一句話：
String date=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(Calendar.getInstance).getTime());
date就是你得到的時間，顯示格式可以根據("yyyy-MM-dd HH:mm:ss")的格式隨意調整
----------------------------------------------------------------
小例6:
在JSP頁面上可以通過一下方法獲取：
function printDate()
{
var today=new Date();
var day=today.getDate();
var month=today.getMonth()+1;
var year=today.getFullYear().toString();
var box1=document.stats.intoDate;
if((month/10)<1)
{
month=("0"+month).toString();
}
if((day/10)<1)
{
day=("0"+today.getDate()).toString();
}
box1.value=year+"-"+month+"-"+day;
}
