Java学习之日期操作

一、日期格式化

 1 import java.text.DateFormat;
 2 import java.text.SimpleDateFormat;
 3 import java.util.Date;
 4 
 5 public class DateDemo {
 6 
 7     public static void main(String[] args) {
 8     Date date=new Date();
 9     
10     DateFormat dateFormat=DateFormat.getDateInstance();
11     
12     System.out.println(dateFormat.format(date));
13     
14     dateFormat=new SimpleDateFormat("yyyy--MM--dd");
15     System.out.println(dateFormat.format(date));
16     }
17 }

自定义格式化SimpleDateFormat字母代表的意义

Letter	Date or Time Component	Presentation	Examples
G	Era designator	Text	AD
y	Year	Year	1996; 96
Y	Week year	Year	2009; 09
M	Month in year (context sensitive)	Month	July; Jul; 07
L	Month in year (standalone form)	Month	July; Jul; 07
w	Week in year	Number	27
W	Week in month	Number	2
D	Day in year	Number	189
d	Day in month	Number	10
F	Day of week in month	Number	2
E	Day name in week	Text	Tuesday; Tue
u	Day number of week (1 = Monday, ..., 7 = Sunday)	Number	1
a	Am/pm marker	Text	PM
H	Hour in day (0-23)	Number	0
k	Hour in day (1-24)	Number	24
K	Hour in am/pm (0-11)	Number	0
h	Hour in am/pm (1-12)	Number	12
m	Minute in hour	Number	30
s	Second in minute	Number	55
S	Millisecond	Number	978
z	Time zone	General time zone	Pacific Standard Time; PST; GMT-08:00
Z	Time zone	RFC 822 time zone	-0800
X	Time zone	ISO 8601 time zone	-08; -0800; -08:00

二、日期字符串转日期对象

 1 import java.text.DateFormat;
 2 import java.text.ParseException;
 3 import java.text.SimpleDateFormat;
 4 
 5 public class DateDemo {
 6 
 7     public static void main(String[] args) throws ParseException {
 8     String strDate="2019/12/30";
 9     
10     DateFormat dateFormat=DateFormat.getDateInstance();
11     
12     System.out.println(dateFormat.parse(strDate));
13     strDate="2019--11--30";
14     dateFormat=new SimpleDateFormat("yyyy--MM--dd");
15     System.out.println(dateFormat.parse(strDate));
16     }
17 }