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This article will explain in detail how to use time format conversion impleDateFormat and Data API in Java. The editor thinks it is very practical, so I share it with you for reference. I hope you can get something after reading this article.

1. Create a parameterless Data object

Date d1=new Date (); / / create a parameterless Data object

System.out.println (D1); / / D1 returns the current time

For example, return:

Sun Nov 14 18:33:05 CST 2021

two。 Create a Data object with parameters

Returns the time available from 08:00:00 milliseconds on January 1, 1970 plus the number of milliseconds passed in.

1s equals 1000ms

One day: 86400000ms

Date d2=new Date (86400000)

System.out.println (d2); / / returned Fri Jan 02 08:00:00 CST 1970 Fri Jan / return: 8: 00 on January 2, 1970 and 08:00:00 on January 1, 1970, one day short package com.example.demo16;import java.util.Date;public class Daterw {public static void main (String [] args) {Date d1=new Date (); System.out.println (D1); / / D1 returns the current time Date d2=new Date (86400000); System.out.println (D2) / / returned Fri Jan 02 08:00:00 CST 1970}} 3.Data object time format conversion:

What we want is 2021-11-14 18:42.

No: Fri Jan 02 08:00:00 CST 1970 (this format)

How do I change it?

Import

Import java.text.SimpleDateFormat

Use: SimpleDateFormat object (create formatted object)

SimpleDateFormat we=new SimpleDateFormat ("yyyy-MM-dd HH:MM:ss SSSS"); / / format yyyy-MM-dd HH:MM:ss SSSS

/ / cannot change letters yyyy:year,MM: month, dd: day, HH: hours, MM: minutes, ss: seconds, SSSS: milliseconds, can be set: SSS, three digits

String wer=we.format (D1); / / use format () to pass in time

System.out.println (wer)

Package com.example.demo16;import java.text.SimpleDateFormat;import java.util.Date;import static java.lang.String.format;public class Daterw {public static void main (String [] args) {SimpleDateFormat we=new SimpleDateFormat ("yyyy-MM-dd HH:MM:ss SSSS"); / / HH:24 hourly calculation, hh:12 hourly calculation, Date d1=new Date (); System.out.println (D1); / / D1 returns the current time Date d2=new Date (86400000) System.out.println (D2); / / returned Fri Jan 02 08:00:00 CST 1970String wer=we.format (D1); System.out.println (wer);}}

Effect picture:

You can also:

SimpleDateFormat we=new SimpleDateFormat ("yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy

Return:

November 14, 2021 19 hours: 05 minutes: 20 seconds 370 milliseconds (this format)

4. Return: a specified parameter: return year / month / day / hour

Direct: this way

SimpleDateFormat we=new SimpleDateFormat ("yyyy year")

Will return:

2021

SimpleDateFormat we=new SimpleDateFormat ("HH hour") / /

Returned:

19 hours

5.API: getTime ()

Long err=d1.getTime (); / / calculation: from 1970-1-1, how many milliseconds have passed to the present, this number is very long, so use the long data type

Package com.example.demo16;import java.text.SimpleDateFormat;import java.util.Date;import static java.lang.String.format;public class Daterw {public static void main (String [] args) {/ / SimpleDateFormat we=new SimpleDateFormat ("yyyy-mm-dd hh:mm:ss SS"); / / SimpleDateFormat we=new SimpleDateFormat ("yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy Date d1=new Date (); System.out.println (D1); / / D1 returns the current time Date d2=new Date (86400000); System.out.println (D2); / / returns ri Jan 02 08:00:00 CST 1970String wer=we.format (D1); System.out.println (wer); long err=d1.getTime () / / calculation: how many milliseconds have elapsed since 1970-1-1, this number is very long, so use the long data type System.out.println (err); long qqq=System.currentTimeMillis (); / / get how many milliseconds System.out.println (qqq) has elapsed since 1970-1-1;}}

Effect:

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