更改Java字符串中的日期格式-Java 学习之路

433

我有 String 代表约会 .

String date_s = "2011-01-18 00:00:00.0";

我想将它转换为 Date 并以 YYYY-MM-DD 格式输出 .

2011-01-18

我怎样才能做到这一点？

好的，根据我在下面找到的答案，这是我尝试过的东西：

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));

但它输出 02011-00-1 而不是所需的 2011-01-18 . 我究竟做错了什么？

16 回答

470

请参考"Date and Time Patterns" . 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();
    }
  } 

}

回复于 2024-05-06T13:49:16+08:00

[编辑包含BalusC的更正] SimpleDateFormat类应该可以解决问题：

String pattern = "yyyy-MM-dd HH:mm:ss.S";
SimpleDateFormat format = new SimpleDateFormat(pattern);
try {
  Date date = format.parse("2011-01-18 00:00:00.0");
  System.out.println(date);
} catch (ParseException e) {
  e.printStackTrace();
}

回复于 2024-05-06T13:49:16+08:00

6

删除一个y表单 SimpleDateFormat dt1 = new SimpleDateFormat("yyyyy-mm-dd"); 应为 SimpleDateFormat dt1 = new SimpleDateFormat("yyyy-mm-dd");

回复于 2024-05-06T13:49:16+08:00

您可以尝试java 8 new date ，更多信息可以在oracle documentation上找到 .

或者你可以尝试旧的

public static Date getDateFromString(String format, String dateStr) {

        DateFormat formatter = new SimpleDateFormat(format);
        Date date = null;
        try {
            date = (Date) formatter.parse(dateStr);
        } catch (ParseException e) {
            e.printStackTrace();
        }

        return date;
    }

    public static String getDate(Date date, String dateFormat) {
        DateFormat formatter = new SimpleDateFormat(dateFormat);
        return formatter.format(date);
    }

回复于 2024-05-06T13:49:16+08:00

137

try
 {
    String date_s = "2011-01-18 00:00:00.0";
    SimpleDateFormat simpledateformat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.S");
    Date tempDate=simpledateformat.parse(date_s);
    SimpleDateFormat outputDateFormat = new SimpleDateFormat("yyyy-MM-dd");           
    System.out.println("Output date is = "+outputDateFormat.format(tempDate));
  } catch (ParseException ex) 
  {
        System.out.println("Parse Exception");
  }

回复于 2024-05-06T13:49:16+08:00

public class SystemDateTest {

    String stringDate;

    public static void main(String[] args) {
        SystemDateTest systemDateTest = new SystemDateTest();
        SimpleDateFormat simpleDateFormat = new SimpleDateFormat("dd-mm-yyyy hh:mm:ss");
        systemDateTest.setStringDate(simpleDateFormat.format(systemDateTest.getDate()));
        System.out.println(systemDateTest.getStringDate());
    }

    public Date getDate() {
        return new Date();
    }

    public String getStringDate() {
        return stringDate;
    }

    public void setStringDate(String stringDate) {
        this.stringDate = stringDate;
    }
}

回复于 2024-05-06T13:49:16+08:00

15
如果字符串碰巧包含时区部分，则使用LocalDateTime#parse()（或ZonedDateTime#parse()）将某个模式中的 String 解析为 LocalDateTime .
```
String oldstring = "2011-01-18 00:00:00.0";
LocalDateTime datetime = LocalDateTime.parse(oldstring, DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.S"));
```
使用LocalDateTime#format()（或ZonedDateTime#format()）将 LocalDateTime 格式化为特定模式的 String .
```
String newstring = datetime.format(DateTimeFormatter.ofPattern("yyyy-MM-dd"));
System.out.println(newstring); // 2011-01-18
```
Or ，当您还没有使用Java 8时，使用SimpleDateFormat#parse()以某种模式将 String 解析为 Date .
```
String oldstring = "2011-01-18 00:00:00.0";
Date date = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.S").parse(oldstring);
```
使用SimpleDateFormat#format()以特定模式将 Date 格式化为 String .
```
String newstring = new SimpleDateFormat("yyyy-MM-dd").format(date);
System.out.println(newstring); // 2011-01-18
```
另见：
- Java string to date conversion
Update ：根据您的尝试失败：模式为 case sensitive . 阅读java.text.SimpleDateFormat javadoc各个部分代表什么 . 因此，例如 M 表示月份， m 表示分钟 . 此外，存在四位数 yyyy ，而不是五位 yyyyy . 仔细看看我在上面发布的代码片段 .
回复于 2024-05-06T13:49:16+08:00

格式化是CASE-SENSITIVE因此使用MM不是mm（这是分钟）和yyyy对于Reference你可以使用以下cheatsheet .

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

回复于 2024-05-06T13:49:16+08:00

为什么不简单地使用它

Date convertToDate(String receivedDate) throws ParseException{
        SimpleDateFormat formatter = new SimpleDateFormat("dd-MM-yyyy");
        Date date = formatter.parse(receivedDate);
        return date;
    }

另外，这是另一种方式：

DateFormat df = new SimpleDateFormat("dd/MM/yyyy");
String requiredDate = df.format(new Date()).toString();

要么

Date requiredDate = df.format(new Date());

干杯!

回复于 2024-05-06T13:49:16+08:00

你也可以使用substring（）

String date_s = "2011-01-18 00:00:00.0";
date_s.substring(0,10);

如果您想在日期前面留出空格，请使用

String date_s = " 2011-01-18 00:00:00.0";
date_s.substring(1,11);

回复于 2024-05-06T13:49:16+08:00

你可以使用：

Date yourDate = new Date();

SimpleDateFormat DATE_FORMAT = new SimpleDateFormat("yyyy-MM-dd");
String date = DATE_FORMAT.format(yourDate);

它完美地运作！

回复于 2024-05-06T13:49:16+08:00

104

答案当然是创建一个SimpleDateFormat对象并使用它来将字符串解析为Date并将Dates格式化为字符串 . 如果你已经尝试过SimpleDateFormat并且它不起作用，那么请显示你的代码以及你可能收到的任何错误 .

附录：格式为String的“mm”与“MM”不同 . 使用MM数月，mm使用数分钟 . 而且，yyyyy与yyyy不同 . 例如 . ，：

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

public class FormateDate {

    public static void main(String[] args) throws ParseException {
        String date_s = "2011-01-18 00:00:00.0";

        // *** note that it's "yyyy-MM-dd hh:mm:ss" not "yyyy-mm-dd hh:mm:ss"  
        SimpleDateFormat dt = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
        Date date = dt.parse(date_s);

        // *** same for the format String below
        SimpleDateFormat dt1 = new SimpleDateFormat("yyyy-MM-dd");
        System.out.println(dt1.format(date));
    }

}

回复于 2024-05-06T13:49:16+08:00

private SimpleDateFormat dataFormat = new SimpleDateFormat("dd/MM/yyyy");

@Override
public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column) {
    if(value instanceof Date) {
        value = dataFormat.format(value);
    }
    return super.getTableCellRendererComponent(table, value, isSelected, hasFocus, row, column);
};

回复于 2024-05-06T13:49:16+08:00

String str = "2000-12-12";
   Date dt = null;
   SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");

    try 
    {
         dt = formatter.parse(str);
    }
    catch (Exception e)
    {
    }

    JOptionPane.showMessageDialog(null, formatter.format(dt));

回复于 2024-05-06T13:49:16+08:00

在Java 8及更高版本中使用 java.time 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);

回复于 2024-05-06T13:49:16+08:00

其他答案是正确的，基本上你的模式中有“y”字符错误 .

时区

还有一个问题......你没有解决时区问题 . 如果您打算UTC，那么您应该这样说 . 如果没有，答案就不完整了 . 如果您想要的只是没有时间的日期部分，那么没有问题 . 但是如果你做了可能涉及时间的进一步工作，那么你应该指定一个时区 .

Joda-Time

这是相同类型的代码，但使用第三方开源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 ) );

跑的时候......

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

回复于 2024-05-06T13:49:16+08:00

更改Java字符串中的日期格式

16 回答

另见：

时区

Joda-Time

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