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preface

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Abstract

This article focuses on the role and constructor of the SimpleDateFormat class.Copy the code

3. The SimpleDateFormat classes

3.1 Purpose of the SimpleDateFormat class

Although we use DateFormat class has been able to carry out date or time formatting, but sometimes does not meet our needs, then we can use DateFormat subclass SimpleDateFormat class, to carry out custom format date or time formatting.

SimpleDateFormat is a concrete class that formats and parses dates in a locale-specific manner. It allows formatting (date -> text), parsing (text -> date), and normalization. The SimpleDateFormat class is basically just two formatting methods, which we’ll talk about below.

3.2 Constructor of the SimpleDateFormat class

SimpleDateFormat has four constructors, which we’ll look at in turn.

Before we introduce the four constructors, let’s look at some pattern letters.

3.2.1 Mode letters:

The letter	Date or time element	The sample
G	Era markers	AD
y	years	1996; 96 yyyy yy
M	Month of the year	July; Jul; 07
w	Weeks of the year	27
W	The number of weeks in a month	2
D	Days of the year	189
d	Days of the month	10
F	Week of the month	2
E	Days of the week	Tuesday; Tue
a	Am/PM	PM
H	Number of hours in a day (0-23)	0
k	Number of hours in a day (1-24)	24
K	Hours in AM/PM (0-11)	0
h	Hours in AM/PM (1-12)	12
m	The number of minutes in an hour	30
s	The number of seconds in minutes	55
S	Number of milliseconds	987

3.2.2 SimpleDateFormat ()

SimpleDateFormat constructs SimpleDateFormat with the default schema and date format notation for the default locale.

 SimpleDateFormat simpleDateFormat1 = new SimpleDateFormat();
 Date date1 = new Date();
 String format1 = simpleDateFormat1.format(date1);
 System.out.println(format1);
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3.2.3 SimpleDateFormat (String pattern)

SimpleDateFormat(String Pattern) Constructs SimpleDateFormat from the given schema and the date format symbol of the default locale.

/ / SimpleDateFormat simpleDateFormat2 = new SimpleDateFormat(" YYYY-MM-DD HH: MM :ss"); / / SimpleDateFormat simpleDateFormat2 = new SimpleDateFormat(" YYYY-MM-DD HH: MM :ss"); Date date2 = new Date(); String format2 = simpleDateFormat2.format(date2); System.out.println(format2);Copy the code

Here are some common patterns:

summary

Today we will first introduce here, tomorrow we continue the SimpleDateFormat class learning, the reason for two to introduce is to write more detailed, I hope to help readers.