我有一个表示日期的字符串。
String date_s = "2011-01-18 00:00:00.0";
我想把它转换成一个日期，并以YYYY-MM-DD格式输出。
2011-01-18
我怎样才能做到这一点呢?
好吧，根据我在下面找到的答案，以下是我尝试过的一些方法:
String date_s = " 2011-01-18 00:00:00.0";
SimpleDateFormat dt = new SimpleDateFormat("yyyyy-mm-dd hh:mm:ss");
Date date = dt.parse(date_s);
SimpleDateFormat dt1 = new SimpleDateFormat("yyyyy-mm-dd");
System.out.println(dt1.format(date));
但是它输出02011-00-1而不是所需的2011-01-18。我做错了什么?
当前回答
格式是大小写敏感的，所以使用MM表示月，而不是MM(这是分钟)和yyyy 作为参考，您可以使用以下备忘单。
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
例子:
"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.SSS'Z'" 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
其他回答
使用java。Java 8及以上版本的时间包:
String date = "2011-01-18 00:00:00.0";
TemporalAccessor temporal = DateTimeFormatter
.ofPattern("yyyy-MM-dd HH:mm:ss.S")
.parse(date); // use parse(date, LocalDateTime::from) to get LocalDateTime
String output = DateTimeFormatter.ofPattern("yyyy-MM-dd").format(temporal);
请参阅此处“日期及时间模式”。http://docs.oracle.com/javase/7/docs/api/java/text/SimpleDateFormat.html
import java.text.SimpleDateFormat;
import java.util.Date;
import java.text.ParseException;
public class DateConversionExample{
public static void main(String arg[]){
try{
SimpleDateFormat sourceDateFormat = new SimpleDateFormat("yyyy-MM-DD HH:mm:ss");
Date date = sourceDateFormat.parse("2011-01-18 00:00:00.0");
SimpleDateFormat targetDateFormat = new SimpleDateFormat("yyyy-MM-dd");
System.out.println(targetDateFormat.format(date));
}catch(ParseException e){
e.printStackTrace();
}
}
}
格式是大小写敏感的，所以使用MM表示月，而不是MM(这是分钟)和yyyy 作为参考，您可以使用以下备忘单。
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
例子:
"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.SSS'Z'" 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
假设您想将2019-12-20 10:50 AM GMT+6:00更改为2019-12-20 10:50 AM 首先，你们要理解日期格式首先，日期格式是 yyyy-MM-dd hh:mm a zzz和第二个日期格式将是yyyy-MM-dd hh:mm a
只要从这个函数返回一个字符串。
public String convertToOnlyDate(String currentDate) {
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm a ");
Date date;
String dateString = "";
try {
date = dateFormat.parse(currentDate);
System.out.println(date.toString());
dateString = dateFormat.format(date);
} catch (ParseException e) {
e.printStackTrace();
}
return dateString;
}
这个函数将返回您想要的答案。如果你想自定义更多，只需从日期格式中添加或删除组件。
其他答案是正确的，基本上你在你的图案中有错误数量的“y”字符。
时区
还有一个问题，你没有提到时区。如果你指的是UTC，那么你应该这么说。如果不是，说明答案不完整。如果您只需要日期部分而不需要时间，那么没有问题。但是如果您要做的进一步工作可能涉及到时间，那么您应该指定一个时区。
乔达时间
下面是相同类型的代码，但是使用了第三方开源的Joda-Time 2.3库
// © 2013 Basil Bourque. This source code may be used freely forever by anyone taking full responsibility for doing so.
String date_s = "2011-01-18 00:00:00.0";
org.joda.time.format.DateTimeFormatter formatter = org.joda.time.format.DateTimeFormat.forPattern( "yyyy-MM-dd' 'HH:mm:ss.SSS" );
// By the way, if your date-time string conformed strictly to ISO 8601 including a 'T' rather than a SPACE ' ', you could
// use a formatter built into Joda-Time rather than specify your own: ISODateTimeFormat.dateHourMinuteSecondFraction().
// Like this:
//org.joda.time.DateTime dateTimeInUTC = org.joda.time.format.ISODateTimeFormat.dateHourMinuteSecondFraction().withZoneUTC().parseDateTime( date_s );
// Assuming the date-time string was meant to be in UTC (no time zone offset).
org.joda.time.DateTime dateTimeInUTC = formatter.withZoneUTC().parseDateTime( date_s );
System.out.println( "dateTimeInUTC: " + dateTimeInUTC );
System.out.println( "dateTimeInUTC (date only): " + org.joda.time.format.ISODateTimeFormat.date().print( dateTimeInUTC ) );
System.out.println( "" ); // blank line.
// Assuming the date-time string was meant to be in Kolkata time zone (formerly known as Calcutta). Offset is +5:30 from UTC (note the half-hour).
org.joda.time.DateTimeZone kolkataTimeZone = org.joda.time.DateTimeZone.forID( "Asia/Kolkata" );
org.joda.time.DateTime dateTimeInKolkata = formatter.withZone( kolkataTimeZone ).parseDateTime( date_s );
System.out.println( "dateTimeInKolkata: " + dateTimeInKolkata );
System.out.println( "dateTimeInKolkata (date only): " + org.joda.time.format.ISODateTimeFormat.date().print( dateTimeInKolkata ) );
// This date-time in Kolkata is a different point in the time line of the Universe than the dateTimeInUTC instance created above. The date is even different.
System.out.println( "dateTimeInKolkata adjusted to UTC: " + dateTimeInKolkata.toDateTime( org.joda.time.DateTimeZone.UTC ) );
运行时……
dateTimeInUTC: 2011-01-18T00:00:00.000Z
dateTimeInUTC (date only): 2011-01-18
dateTimeInKolkata: 2011-01-18T00:00:00.000+05:30
dateTimeInKolkata (date only): 2011-01-18
dateTimeInKolkata adjusted to UTC: 2011-01-17T18:30:00.000Z
