Java 使用SimpleDateFormat格式化日期

Java 使用SimpleDateFormat格式化日期，这里只涉及最实用的方面。

用途

用于格式化日期和解析日期类型字符串。

formatting (date -> text), parsing (text -> date)

构造函数

SimpleDateFormat(String pattern)

Constructs a
 
SimpleDateFormat
 using the given pattern and the default date format symbols for the default locale.

日期和时间模式(pattern)

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	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

常用模式

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
"yyyy-MM-dd'T'HH:mm:ss.SSSXXX"	2001-07-04T12:08:56.235-07:00
"YYYY-'W'ww-u"	2001-W27-3
"YYYY-MM-dd"	2018-01-24

举例

package com.dylan.datatype;

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

/**
 * @author xusucheng
 * @create 2018-01-24
 **/
public class SimpleDateFormatTest {
    public static void main(String[] args) {
        //create date format
        SimpleDateFormat sdf1 = new SimpleDateFormat("yyyy-MM-dd");
        SimpleDateFormat sdf2 = new SimpleDateFormat("yyyy/M/d");

        //convert date to specific format string
        Date date = new Date();
        System.out.println(sdf1.format(date));

        //convert string to date
        String dateStr="2018/1/24";
        try {
            System.out.println(sdf2.parse(dateStr));
        } catch (ParseException e) {
            e.printStackTrace();
        }
    }
}

输出：

2018-01-24
Wed Jan 24 00:00:00 CST 2018

注意：

SimpleDateFormat是非线程安全的，建议为每一个线程单独创建格式化实例。