java.text下的SimpleDateFormat类

开发中经常会用到格式化的时间，SimpleDateFormat类就可以轻松过解决这些问题，引用Oracle官方文档介绍：

SimpleDateFormat is a concrete class for formatting and parsing dates in a locale-sensitive manner. It allows for formatting (date -> text), parsing (text -> date), and normalization.

即SimpleDateFormat是一个可以以局部敏感方式格式化、解析日期的一个具体的类, 支持date --> String 的格式化 、 String --> date的解析 、标准化(默认方式)； 看完就知道为什么么是局部敏感了~

 

The following pattern letters are defined (all other characters from 'A' to 'Z' and from 'a' to 'z' are reserved):

Letter	Date or Time Component	Presentation	Examples
G	Era designator	Text	AD
y	Year	Year	1996; 96
M	Month in year	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 in week	Text	Tuesday; Tue
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

 

形如：SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日");

双引号中的字符串指定时间日期的格式，使用单引号 ' ' 可以避免被翻译，非保留的字符都不会被翻译，会被直接复制到输出字符串中 或 在解析过程中与输入字符串匹配。

 

Examples:

Date and Time Pattern	Result
"yyyy.MM.dd G 'at' HH:mm:ss z"	2001.07.04 AD at 12:08:56 PDT
"EEE, MMM d, ' ' yy"	Wed, Jul 4, '01
"h:mm a"	12:08 PM
"hh 'o''clock' a, zzzz"	12 o'clock PM, Pacific Daylight Time
"K:mm a, z"	0:08 PM, PDT
"yyyyy.MMMMM.dd GGG hh:mm aaa"	02001.July.04 AD 12:08 PM
"EEE, d MMM yyyy HH:mm:ss Z"	Wed, 4 Jul 2001 12:08:56 -0700
"yyMMddHHmmssZ"	010704120856-0700
"yyyy-MM-dd'T'HH:mm:ss.SSSZ"	2001-07-04T12:08:56.235-0700

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附：

//String—>Date

String  time = “2018-10-15”；
try{
    SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
    Date date = sdf.parse(time);
}catch(ParseException e){
    e.printStackTrace();
}

//Date—>String

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd"); 
Date date = new Date(); 
String str = sdf.format(date);