在 Java 中使用不同的格式将字符串解析为日期
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Parse String to Date with Different Format in Java
提问by Gnaniyar Zubair
I want to convert Stringto Datein different formats.
我想转换String为Date不同的格式。
For example,
例如，
I am getting from user,
我从用户那里得到，
String fromDate = "19/05/2009"; // i.e. (dd/MM/yyyy) format
I want to convert this fromDateas a Date object of "yyyy-MM-dd"format
我想将其转换fromDate为"yyyy-MM-dd"格式的 Date 对象
How can I do this?
我怎样才能做到这一点？
采纳答案by Michael Myers
Take a look at SimpleDateFormat. The code goes something like this:
看看SimpleDateFormat。代码是这样的：
SimpleDateFormat fromUser = new SimpleDateFormat("dd/MM/yyyy");
SimpleDateFormat myFormat = new SimpleDateFormat("yyyy-MM-dd");
try {
String reformattedStr = myFormat.format(fromUser.parse(inputString));
} catch (ParseException e) {
e.printStackTrace();
}
回答by Matt
Check the javadocs for java.text.SimpleDateFormatIt describes everything you need.
检查 javadocsjava.text.SimpleDateFormat它描述了你需要的一切。
回答by Agora
Use the SimpleDateFormatclass:
使用SimpleDateFormat类：
private Date parseDate(String date, String format) throws ParseException
{
SimpleDateFormat formatter = new SimpleDateFormat(format);
return formatter.parse(date);
}
Usage:
用法：
Date date = parseDate("19/05/2009", "dd/MM/yyyy");
For efficiency, you would want to store your formatters in a hashmap. The hashmap is a static member of your util class.
为了提高效率，您可能希望将格式化程序存储在哈希图中。hashmap 是 util 类的静态成员。
private static Map<String, SimpleDateFormat> hashFormatters = new HashMap<String, SimpleDateFormat>();
public static Date parseDate(String date, String format) throws ParseException
{
SimpleDateFormat formatter = hashFormatters.get(format);
if (formatter == null)
{
formatter = new SimpleDateFormat(format);
hashFormatters.put(format, formatter);
}
return formatter.parse(date);
}
回答by James McMahon
While SimpleDateFormatwill indeed work for your needs, additionally you might want to check out Joda Time, which is apparently the basis for the redone Date library in Java 7. While I haven't used it a lot, I've heard nothing but good things about it and if your manipulating dates extensively in your projects it would probably be worth looking into.
虽然SimpleDateFormat确实可以满足您的需求，但您可能还想查看Joda Time，它显然是 Java 7 中重做 Date 库的基础。虽然我没有经常使用它，但我只听到了一些好消息关于它，如果你在你的项目中广泛地操纵日期，它可能值得研究。
回答by Ritesh Kaushik
Convert a string date to java.sql.Date
将字符串日期转换为 java.sql.Date
String fromDate = "19/05/2009";
DateFormat df = new SimpleDateFormat("dd/MM/yyyy");
java.util.Date dtt = df.parse(fromDate);
java.sql.Date ds = new java.sql.Date(dtt.getTime());
System.out.println(ds);//Mon Jul 05 00:00:00 IST 2010
回答by Khalid Habib
Simple way to format a date and convert into string
格式化日期并转换为字符串的简单方法
Date date= new Date();
String dateStr=String.format("%td/%tm/%tY", date,date,date);
System.out.println("Date with format of dd/mm/dd: "+dateStr);
output:Date with format of dd/mm/dd: 21/10/2015
输出：日期格式为 dd/mm/dd：21/10/2015
回答by Basil Bourque
tl;dr
tl;博士
LocalDate.parse(
"19/05/2009" ,
DateTimeFormatter.ofPattern( "dd/MM/uuuu" )
)
Details
细节
The other Answers with java.util.Date, java.sql.Date, and SimpleDateFormatare now outdated.
其他带有java.util.Date、java.sql.Date和 的答案SimpleDateFormat现已过时。
LocalDate
LocalDate
The modern way to do date-time is work with the java.time classes, specifically LocalDate. The LocalDateclass represents a date-only value without time-of-day and without time zone.
处理日期时间的现代方法是使用 java.time 类，特别是LocalDate. 该LocalDate级表示没有时间一天和不同时区的日期，唯一的价值。
DateTimeFormatter
DateTimeFormatter
To parse, or generate, a String representing a date-time value, use the DateTimeFormatterclass.
要解析或生成表示日期时间值的字符串，请使用DateTimeFormatter该类。
DateTimeFormatter f = DateTimeFormatter.ofPattern( "dd/MM/uuuu" );
LocalDate ld = LocalDate.parse( "19/05/2009" , f );
Do not conflate a date-time object with a String representing its value. A date-time object has noformat, while a String does. A date-time object, such as LocalDate, can generatea String to represent its internal value, but the date-time object and the String are separate distinct objects.
不要将日期时间对象与表示其值的字符串混为一谈。一个日期时间对象有没有格式，而字符串中。日期时间对象（例如LocalDate）可以生成字符串来表示其内部值，但日期时间对象和字符串是不同的独立对象。
You can specify any custom format to generate a String. Or let java.time do the work of automatically localizing.
您可以指定任何自定义格式来生成字符串。或者让 java.time 做自动本地化的工作。
DateTimeFormatter f =
DateTimeFormatter.ofLocalizedDate( FormatStyle.FULL )
.withLocale( Locale.CANADA_FRENCH ) ;
String output = ld.format( f );
Dump to console.
转储到控制台。
System.out.println( "ld: " + ld + " | output: " + output );
ld: 2009-05-19 | output: mardi 19 mai 2009
ld: 2009-05-19 | 输出：2009 年狂欢节 19 月
About java.time
关于java.time
The java.timeframework is built into Java 8 and later. These classes supplant the troublesome old legacydate-time classes such as java.util.Date, Calendar, & SimpleDateFormat.
该java.time框架是建立在Java 8和更高版本。这些类取代了麻烦的旧的遗留日期时间类，例如java.util.Date, Calendar, & SimpleDateFormat。
The Joda-Timeproject, now in maintenance mode, advises migration to the java.timeclasses.
现在处于维护模式的Joda-Time项目建议迁移到java.time类。
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
要了解更多信息，请参阅Oracle 教程。并在 Stack Overflow 上搜索许多示例和解释。规范是JSR 310。
You may exchange java.timeobjects directly with your database. Use a JDBC drivercompliant with JDBC 4.2or later. No need for strings, no need for java.sql.*classes.
您可以直接与您的数据库交换java.time对象。使用符合JDBC 4.2或更高版本的JDBC 驱动程序。不需要字符串，不需要类。java.sql.*
Where to obtain the java.time classes?
从哪里获得 java.time 类？
- Java SE 8, Java SE 9, and later
- Built-in.
- Part of the standard Java API with a bundled implementation.
- Java 9 adds some minor features and fixes.
- Java SE 6and Java SE 7
- Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
- Android
- Later versions of Android bundle implementations of the java.time classes.
- For earlier Android (<26), the ThreeTenABPproject adapts ThreeTen-Backport(mentioned above). See How to use ThreeTenABP….
- Java SE 8、Java SE 9及更高版本
- 内置。
- 具有捆绑实现的标准 Java API 的一部分。
- Java 9 添加了一些小功能和修复。
- Java SE 6和Java SE 7
- 多的java.time功能后移植到Java 6和7在ThreeTen-反向移植。
- 安卓
- 更高版本的 Android 捆绑实现 java.time 类。
- 对于早期的 Android（<26），ThreeTenABP项目采用了ThreeTen-Backport（上面提到过）。请参阅如何使用ThreeTenABP ...。
The ThreeTen-Extraproject extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.
该ThreeTen-额外项目与其他类扩展java.time。该项目是未来可能添加到 java.time 的试验场。你可能在这里找到一些有用的类，比如Interval，YearWeek，YearQuarter，和更多。
回答by Dulith De Costa
A Dateobject has no format, it is a representation. The date can be presented by a Stringwith the format you like.
甲Date对象具有无格式，它是一个表示。日期可以String用您喜欢的格式显示。
E.g. "yyyy-MM-dd", "yy-MMM-dd", "dd-MMM-yy" and etc.
例如“ yyyy-MM-dd”、“ yy-MMM-dd”、“ dd-MMM-yy”等。
To acheive this you can get the use of the SimpleDateFormat
要实现这一点，您可以使用 SimpleDateFormat
Try this,
尝试这个，
String inputString = "19/05/2009"; // i.e. (dd/MM/yyyy) format
SimpleDateFormat fromUser = new SimpleDateFormat("dd/MM/yyyy");
SimpleDateFormat myFormat = new SimpleDateFormat("yyyy-MM-dd");
try {
Date dateFromUser = fromUser.parse(inputString); // Parse it to the exisitng date pattern and return Date type
String dateMyFormat = myFormat.format(dateFromUser); // format it to the date pattern you prefer
System.out.println(dateMyFormat); // outputs : 2009-05-19
} catch (ParseException e) {
e.printStackTrace();
}
This outputs : 2009-05-19
此输出：2009-05-19
回答by milad salimi
Suppose that you have a string like this :
假设你有一个这样的字符串：
String mDate="2019-09-17T10:56:07.827088"
Now we want to change this Stringformat separate date and time in Javaand Kotlin.
现在我们想String在Java和Kotlin 中改变这种格式，将日期和时间分开。
JAVA:
爪哇：
we have a method for extract date:
我们有一种提取日期的方法：
public String getDate() {
try {
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS", Locale.US);
Date date = dateFormat.parse(mDate);
dateFormat = new SimpleDateFormat("MM/dd/yyyy", Locale.US);
return dateFormat.format(date);
} catch (ParseException e) {
e.printStackTrace();
}
return null;
}
Returnis this : 09/17/2019
Return这是 : 09/17/2019
And we have method for extract time:
我们有提取时间的方法：
public String getTime() {
try {
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS", Locale.US);
Date date = dateFormat.parse(mCreatedAt);
dateFormat = new SimpleDateFormat("h:mm a", Locale.US);
return dateFormat.format(date);
} catch (ParseException e) {
e.printStackTrace();
}
return null;
}
Returnis this :10:56 AM
Return这是：上午 10:56
KOTLIN:
科特林：
we have a function for extract date:
我们有一个提取日期的函数：
fun getDate(): String? {
var dateFormat = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS", Locale.US)
val date = dateFormat.parse(mDate!!)
dateFormat = SimpleDateFormat("MM/dd/yyyy", Locale.US)
return dateFormat.format(date!!)
}
Returnis this : 09/17/2019
Return这是 : 09/17/2019
And we have method for extract time:
我们有提取时间的方法：
fun getTime(): String {
var dateFormat = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS", Locale.US)
val time = dateFormat.parse(mDate!!)
dateFormat = SimpleDateFormat("h:mm a", Locale.US)
return dateFormat.format(time!!)
}
Returnis this :10:56 AM
Return这是：上午 10:56
