java怎么进行日期运算_java关于日期的运算等处理方法
java关于日期的运算等处理方法
日期问题
1、获取服务器端当前日期：
2、获取当前年、月、日：
int thisYear = myDate.getYear() + 1900;
int thisMonth = myDate.getMonth() + 1;
int thisDate = myDate.getDate();%>
3、按本地时区输出当前日期
out.println(myDate.toLocaleString());%>
输出格式为： 0000-00-00
4、获取数据库中字段名为”publish_time“、类型为Datetime的值
5、按照指定格式打印日期
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 0000.00.00 at 00:00:00 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
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
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 X days.
8、日期的加减运算
方法：用Calendar类的add()方法
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("
");
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
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
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("
");
out.println("Cyc ends at " + t1);
out.println("
");
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.
//获得当前日期时间
String nowDate = TimeString.getNowTime("yyyy-MM-dd");
String nowTime = TimeString.getNowTime("HH:mm:ss");
String nowDateTime = TimeString.getNowTime("yyyy-MM-dd HH:mm:ss");
out.println("nowDate: "+nowDate);
out.println("nowTime: "+nowTime);
out.println("nowDateTime: "+nowDateTime);
%>
//******************************************************
//GUI 或java 小程序获得得当前日期
public class Test()
{
public static void main(String abc[])
{
//直接包名点类名点方法名使用
System.out.println("nowDate: "+com.Mamak.util.TimeString.getNowTime("yyyy-MM-dd"));
System.out.println("nowTime: "+com.Mamak.util.TimeString.getNowTime("HH:mm:ss"));
System.out.println("nowDateTime: "+com.Mamak.util.TimeString.getNowTime("yyyy-MM-dd HH:mm:ss"));
}
}
//******************************************************
//获得时间的bean 文件名 TimeString.java
package com.Mamak.util;
import java.text.SimpleDateFormat;
import java.util.Calendar;
public class TimeString
{
public TimeString()
{
}
public static String getNowTime(String timeFormat)
{
SimpleDateFormat lformat = new SimpleDateFormat(timeFormat);
Calendar now = Calendar.getInstance();
String nowstr = lformat.format(now.getTime());
return nowstr;
}
public static String getNotTime()
{
return getNowTime("yyyy-MM-dd");
}
}
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