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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