Java从入门到实战之（23）时间处理之练习

1、格式化时间（SimpleDateFormat）

如何使用 SimpleDateFormat 类的 format(date) 方法来格式化时间？

package Java_Learn.File;

import java.text.SimpleDateFormat;
import java.util.Date;

public class Main1 {
    public static void main(String[] args) {
        Date date = new Date();
        String strDateFormat = "yyyy-MM-dd HH:mm:ss";
        String msg="当前时间是:";
        formatTime(msg,date,strDateFormat);
    }
    private static void formatTime(String msg,Date date,String strDateFormat)
    {
        SimpleDateFormat simpleDateFormat=new SimpleDateFormat(strDateFormat);
        System.out.println(msg+simpleDateFormat.format(date));
    }
}

结果：

"C:Program FilesJavajdk1.8.0_221injava.exe" "-javaagent:C:Program FilesJetBrainsIntelliJ IDEA 2019.3.3libidea_rt.jar=52237:C:Program FilesJetBrainsIntelliJ IDEA 2019.3.3in" -Dfile.encoding=UTF-8 -classpath "C:Program FilesJavajdk1.8.0_221jrelibcharsets.jar;C:Program FilesJavajdk1.8.0_221jrelibdeploy.jar;C:Program FilesJavajdk1.8.0_221jrelibextaccess-bridge-64.jar;C:Program FilesJavajdk1.8.0_221jrelibextcldrdata.jar;C:Program FilesJavajdk1.8.0_221jrelibextdnsns.jar;C:Program FilesJavajdk1.8.0_221jrelibextjaccess.jar;C:Program FilesJavajdk1.8.0_221jrelibextjfxrt.jar;C:Program FilesJavajdk1.8.0_221jrelibextlocaledata.jar;C:Program FilesJavajdk1.8.0_221jrelibext
ashorn.jar;C:Program FilesJavajdk1.8.0_221jrelibextsunec.jar;C:Program FilesJavajdk1.8.0_221jrelibextsunjce_provider.jar;C:Program FilesJavajdk1.8.0_221jrelibextsunmscapi.jar;C:Program FilesJavajdk1.8.0_221jrelibextsunpkcs11.jar;C:Program FilesJavajdk1.8.0_221jrelibextzipfs.jar;C:Program FilesJavajdk1.8.0_221jrelibjavaws.jar;C:Program FilesJavajdk1.8.0_221jrelibjce.jar;C:Program FilesJavajdk1.8.0_221jrelibjfr.jar;C:Program FilesJavajdk1.8.0_221jrelibjfxswt.jar;C:Program FilesJavajdk1.8.0_221jrelibjsse.jar;C:Program FilesJavajdk1.8.0_221jrelibmanagement-agent.jar;C:Program FilesJavajdk1.8.0_221jrelibplugin.jar;C:Program FilesJavajdk1.8.0_221jrelib
esources.jar;C:Program FilesJavajdk1.8.0_221jrelib
t.jar;C:appWorkSpace	argetclasses;C:Program Files (x86)scalalibscala-actors-2.11.0.jar;C:Program Files (x86)scalalibscala-actors-migration_2.11-1.1.0.jar;C:Program Files (x86)scalalibscala-library.jar;C:Program Files (x86)scalalibscala-parser-combinators_2.11-1.0.1.jar;C:Program Files (x86)scalalibscala-reflect.jar;C:Program Files (x86)scalalibscala-swing_2.11-1.0.1.jar;C:Program Files (x86)scalalibscala-xml_2.11-1.0.1.jar;C:
epositoryorgscala-langscala-library2.11.0scala-library-2.11.0.jar" Java_Learn.File.Main1
当前时间是:2020-10-26 11:42:24

Process finished with exit code 0

2、当前时间

如何获取当前时间？

package Java_Learn.File;

import java.text.SimpleDateFormat;
import java.util.Date;

public class Main1 {
    public static void main(String[] args) {
        Date date = new Date();
        String strDateFormat = "yyyy-MM-dd HH:mm:ss";
        String msg="当前时间是:";
        formatTime(msg,date,strDateFormat);
        formatTime1(msg,date,strDateFormat);
    }
    private static void formatTime(String msg,Date date,String strDateFormat)
    {
        SimpleDateFormat simpleDateFormat=new SimpleDateFormat(strDateFormat);
        System.out.println(msg+simpleDateFormat.format(date));
    }
    private static void formatTime1(String msg,Date date,String strDateFormat)
    {
        SimpleDateFormat simpleDateFormat=new SimpleDateFormat(strDateFormat);
        simpleDateFormat.applyPattern(strDateFormat);// a为am/pm的标记
        System.out.println(msg+simpleDateFormat.format(date));
    }
}

结果：

"C:Program FilesJavajdk1.8.0_221injava.exe" "-javaagent:C:Program FilesJetBrainsIntelliJ IDEA 2019.3.3libidea_rt.jar=52284:C:Program FilesJetBrainsIntelliJ IDEA 2019.3.3in" -Dfile.encoding=UTF-8 -classpath "C:Program FilesJavajdk1.8.0_221jrelibcharsets.jar;C:Program FilesJavajdk1.8.0_221jrelibdeploy.jar;C:Program FilesJavajdk1.8.0_221jrelibextaccess-bridge-64.jar;C:Program FilesJavajdk1.8.0_221jrelibextcldrdata.jar;C:Program FilesJavajdk1.8.0_221jrelibextdnsns.jar;C:Program FilesJavajdk1.8.0_221jrelibextjaccess.jar;C:Program FilesJavajdk1.8.0_221jrelibextjfxrt.jar;C:Program FilesJavajdk1.8.0_221jrelibextlocaledata.jar;C:Program FilesJavajdk1.8.0_221jrelibext
ashorn.jar;C:Program FilesJavajdk1.8.0_221jrelibextsunec.jar;C:Program FilesJavajdk1.8.0_221jrelibextsunjce_provider.jar;C:Program FilesJavajdk1.8.0_221jrelibextsunmscapi.jar;C:Program FilesJavajdk1.8.0_221jrelibextsunpkcs11.jar;C:Program FilesJavajdk1.8.0_221jrelibextzipfs.jar;C:Program FilesJavajdk1.8.0_221jrelibjavaws.jar;C:Program FilesJavajdk1.8.0_221jrelibjce.jar;C:Program FilesJavajdk1.8.0_221jrelibjfr.jar;C:Program FilesJavajdk1.8.0_221jrelibjfxswt.jar;C:Program FilesJavajdk1.8.0_221jrelibjsse.jar;C:Program FilesJavajdk1.8.0_221jrelibmanagement-agent.jar;C:Program FilesJavajdk1.8.0_221jrelibplugin.jar;C:Program FilesJavajdk1.8.0_221jrelib
esources.jar;C:Program FilesJavajdk1.8.0_221jrelib
t.jar;C:appWorkSpace	argetclasses;C:Program Files (x86)scalalibscala-actors-2.11.0.jar;C:Program Files (x86)scalalibscala-actors-migration_2.11-1.1.0.jar;C:Program Files (x86)scalalibscala-library.jar;C:Program Files (x86)scalalibscala-parser-combinators_2.11-1.0.1.jar;C:Program Files (x86)scalalibscala-reflect.jar;C:Program Files (x86)scalalibscala-swing_2.11-1.0.1.jar;C:Program Files (x86)scalalibscala-xml_2.11-1.0.1.jar;C:
epositoryorgscala-langscala-library2.11.0scala-library-2.11.0.jar" Java_Learn.File.Main1
当前时间是:2020-10-26 11:44:53
当前时间是:2020-10-26 11:44:53

Process finished with exit code 0

3、年、月、日等时间的处理

如何获取年、月、日等时间格式？

import java.util.Calendar;
 
public class Main {
    public static void main(String[] args) {
        Calendar cal = Calendar.getInstance();
        int day = cal.get(Calendar.DATE);
        int month = cal.get(Calendar.MONTH) + 1;
        int year = cal.get(Calendar.YEAR);
        int dow = cal.get(Calendar.DAY_OF_WEEK);
        int dom = cal.get(Calendar.DAY_OF_MONTH);
        int doy = cal.get(Calendar.DAY_OF_YEAR);
 
        System.out.println("当期时间: " + cal.getTime());
        System.out.println("日期: " + day);
        System.out.println("月份: " + month);
        System.out.println("年份: " + year);
        System.out.println("一周的第几天: " + dow);  // 星期日为一周的第一天输出为 1，星期一输出为 2，以此类推
        System.out.println("一月中的第几天: " + dom);
        System.out.println("一年的第几天: " + doy);
    }
}

结果：

当期时间: Fri Mar 27 21:44:15 CST 2015
日期: 27
月份: 3
年份: 2015
一周的第几天: 6
一月中的第几天: 27
一年的第几天: 86

4、时间戳转换成时间

如何使用 SimpleDateFormat 类的 format() 方法将时间戳转换成时间。

日期和时间模式(注意大小写，代表的含义是不同的)：

  • yyyy：年
  • MM：月
  • dd：日
  • hh：1~12小时制(1-12)
  • HH：24小时制(0-23)
  • mm：分
  • ss：秒
  • S：毫秒
  • E：星期几
  • D：一年中的第几天
  • F：一月中的第几个星期(会把这个月总共过的天数除以7)
  • w：一年中的第几个星期
  • W：一月中的第几星期(会根据实际情况来算)
  • a：上下午标识
  • k：和HH差不多，表示一天24小时制(1-24)
  • K：和hh差不多，表示一天12小时制(0-11)
  • z：表示时区
import java.text.SimpleDateFormat;
import java.util.Date;
 
public class Main{
    public static void main(String[] args){
        Long timeStamp = System.currentTimeMillis();  //获取当前时间戳
        SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        String sd = sdf.format(new Date(Long.parseLong(String.valueOf(timeStamp))));      // 时间戳转换成时间
        System.out.println("格式化结果：" + sd);
 
        SimpleDateFormat sdf2 = new SimpleDateFormat("yyyy 年 MM 月 dd 日 HH 时 mm 分 ss 秒");
        String sd2 = sdf2.format(new Date(Long.parseLong(String.valueOf(timeStamp))));
        System.out.println("格式化结果：" + sd2);
   }
}

结果：

格式化结果：2018-07-10 12:17:34
格式化结果：2018 年 07 月 10 日 12 时 17 分 34 秒
作者：大码王

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原文地址：https://www.cnblogs.com/huanghanyu/p/13877699.html