Java Date format - java

I have a spring web application that runs in Tomcat. I must set the date and number format for my application to a special format.
Can I set the format in any descriptor to the special in my application or I can set the all system format only?
I want to use this pattern: yyyy.mm.dd.
This code is wrong because it's not a standard locale pattern:
String currentDate = SimpleDateFormat.getDateTimeInstance(DateFormat.SHORT, DateFormat.SHORT, Locale.UK).format(new Date());
But I don't want type the pattern everywhere in the application, I want set the pattern once.
I want if I type this code:
String currentDate = SimpleDateFormat.getDateInstance(DateFormat.SHORT).format(new Date());
The result is: 2010.08.04.
Is it possible?

java.util.Date objects do not have a format by themselves (they only represent the date and time value, just like integers only represent a number value and don't know anything about formatting numbers).
There is no system-wide default date format setting. When you print a Date object by (implicitly or explicitly) calling toString() on it, it will be printed with a fixed, default format that you can't change:
System.out.println(new Date());
// Example output: Wed Aug 04 09:46:57 CEST 2010
If you want to show a date with a specific format, use a java.text.DateFormat object to format it. For example:
DateFormat df = new SimpleDateFormat("dd-MM-yyyy HH:mm:ss");
System.out.println(df.format(new Date()));
// Example output: 04-08-2010 09:48:47

You can absolutely format a date any way you want, no matter if you use Spring or not. First though make sure that you really need a "special formatting", not just a format that is default for a certain locale (like deCH or svSE or enGB) because if you just want to convert a date to your countries native date formatting you can simply use
String currentDate = SimpleDateFormat.getDateTimeInstance(DateFormat.SHORT, DateFormat.SHORT, Locale.UK).format(new Date());
And if you really want a custom formatting, you can do like this
String currentDateMyFormat = new SimpleDateFormat("dd:MMM:yy HH.mm").format(new Date());
Of course you can reverse the process (from String to Date) by replacing format with parse.
Hope this answers your question because just like Xu before me, I am not sure I understood your question completely ;)

Since you're talking about doing something application-wide, let me remind you to be cautious with any java.text.Format subclass (including DateFormat, SimpleDateFormat, etc.). As noted in the Javadoc, Formats are generally not thread-safe. I know from personal experience that DateFormats are not.
Therefore, if you're considering setting something up for use across your application, I recommend only defining the format String and sharing it around the application. Instances of a Format class are best-defined in a thread-safe manner, such as on the stack of a method call.

Related

Java - SimpleDateFormat unexpected parsing behaviour

I'm reading information from a file (.csv) that will be inserted to a database after validation and approval from the end user. The text file is read, validated and its information loaded to a List containing forms which are used to check if the data already exist in database.
The problem arises when parsing the String to Date. The SimpleDateFormat.parse() method returns an unexpected date format even when the pattern for SimpleDateFormat is "yyyy-MM-dd".
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
dateFormat.setLenient(false);
Parsing the loaded values to the travel object:
travel.setDate( dateFormat.parse( form.getTravelDate() ));
In debugger the form shows the date as:
"2012-12-12"
It is read as intended. However when parsed becomes:
Wed Dec 12 00:00:00 CST 2012
I've spent the whole day trying to solve this but I'm out of ideas at this point. Afaik the pattern is alright and I've tried adding a locale to no avail.
Edit: the problem is when I need to insert the values to the database using Hibernate. The not desired format also ends up showing in the Database.
The data is show in a .jsp page using
HttpServletRequest("table",travelList);
The date format I don't need shows here, when in the past this issue never happened. At last the information is sent to the database where the problem persists.
No, it "becomes" a java.util.Date value. If you're then converting it back to a string by calling Date.toString(), you should consult the Date.toString() documentation for what to expect.
The value stored in the Date is just a point in time - the number of milliseconds since the Unix epoch. There's no format in there, no time zone etc. It also doesn't know that it was only a date value rather than a date and time (the naming of Date is one of the many unfortunate aspects of the API).
It's crucial that you mentally separate "the result of the parse operation" from "the string value that is used to represent that result if I call toString"".
I'd also advise you to set the time zone on your SimpleDateFormat to UTC when parsing a date - that way you know that you can't possibly have any ambiguous or skipped times leading to hard-to-predict behaviour. (Of course, you then need to know that you'll have parsed the date to "the start of the UTC date" and handle it appropriately elsewhere.)
You need to use the formatter when printing the Date as well.
dateFormat.format( travel.getDate() );
When your parse the String using a DateFormat, you get a complete Date object with the time units missing in the string initialized to zero. In your example, that's hours, minutes and seconds.
By default, if you do not use a formatter, Date's default string representation (provided by its toString() method) gets printed.
Parsing doesn't mean it format, it simply parse it as text to a java.util.Date object. See parse method in documentation.
You need to use the format method.
dateFormat.format(travel.getDate())
See documentation for more details.
if form.getTravelDate() is returning String then First Parse the Date from String
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
dateFormat.setLenient(false);
Date parsedDate=dateFormat.parse(form.getTravelDate());
// Here parsedDate is in form Wed Dec 12 00:00:00 CST 2012
Now Format the Date using the Same SImpleDateFormat to get the desired output
System.out.println(dateFormat.format(parsedDate));
Your Desired Output
2012-12-12
Update
Assuming data Type of Columns in which we insert this data in Database is of Date Type not varchar then use the below statement
travel.setDate(dateFormat.format(parsedDate));
As I understand parse method returns Date. Below is the parse method syntax.
public Date parse(String source)
throws ParseException
So, you need to parse the string date and store into a Date variable. Then format the Date variable using SimpleDateFormat.
//getTravelDate is "2012-12-12"
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
dateFormat.setLenient(false);
Date dtObj=new Date();
dtObj=dateFormat.parse(form.getTravelDate()); //Store in date variable
System.out.println(dateFormat.format(dtObj)); // Now format the date object
The final output will be 2012-12-12. Hope it will help you.

How to present a date that can be parsed by any DateTimeFormatter pattern in Java?

I'm working with a software that uses a lot of DateTimeFormat parsing, in order to minimize the errors, I wonder if I can present the date String in a certain way that it can be parsed by any DateTimeFormat pattern. Ideally it should work as follows:
String date = "...."
DateTimeFormatter format = DateTimeFormat.forPattern(any pattern I want);
DateTime result = format.parseDateTime(date);
Or does the date have to follow the pattern? Thanks for your help
No, you can not get one size fits all. Think if your string is not a legal date at all, something like "hello", how are you going to parse it?
java.time
Java 8 and later includes the java.time framework (Tutorial). The java.time formatter’s pattern may contain []to mark optional parts. This gives you some flexibility. Say you use format:
M[M]['/']['-']['.']d[d]['/']['-']['.']yyyy[' ']['T'][' ']h[h]:mm:ss
So in this case your string may have one or two digits specifying month, day and hour. Month, day and year may be separated by ., - or / and so forth. For example with format above the following strings will be parsed successfully:
1/10/1995 9:34:45
01-10-1995 09:34:45
01.10.1995T09:34:45
…and so forth.
I wrote a utility that has a set of patterns. Once it gets a String it tries to parse it with all the patterns in the set and sees if it succeeds with one of them. If you write such a set of patterns correctly you may ensure that your util supports any possible String that denotes a valid date.
SimpleDateFromat let you set your own date patters. for example dd/mm/yyyy, mm/dd/yyyy, yyyy-mm-dd etc..
This link can give you a better understanding about date patterns and how to use it
use SimpleDateFormat
SimpleDateFormat sdf=new SimpleDateFormat("dd/MM/yyyy");
Date d=sdf.parse("07/12/2014");

Java printf with date and month

System.out.printf("Time: %d-%d %02d:%02d" +
calendar.get(Calendar.DAY_OF_MONTH),
calendar.get(Calendar.MONTH),
calendar.get(Calendar.HOUR_OF_DAY),
calendar.get(Calendar.MINUTE);
That is the code a friend showed me, but how do I get the date to appear in a Format like November 1?
This is how to do it:
DateFormat dateFormat = new SimpleDateFormat( "MMMMM d" );
Calendar calendar = new GregorianCalendar(); // The date you want to format
Date dateToFormat = calendar.getTime();
String formattedDate = dateFormat.format( dateToFormat );
System.out.println( formattedDate );
Date d = new Date();
System.out.printf("%s %tB %<td", "Today", d);
// output :
// Today november 01
%tB for Locale-specific full month name, e.g. "January", "February".
%<td d for Day of month, formatted as two digits with leading zeros as necessary, < for reuse the last parameter.
The DateFormat answer is the way to do this. The printf answer is also good although does not provide locale-specific formats (it provides language-specific names but does not use e.g. the day/month/year ordering that the current locale uses).
You asked in a comment:
Can I do it with the calendar.get(Calendar.MONTH) etc method? Or do I have to use date format?
You don't have to use the other methods here, but if you want to use the Calender fields, it is up to you to convert the numeric values they provide to strings like "Tuesday" or "November". For that you can use the built in DateFormatSymbols, which provides internationalized strings from numbers for dates, in the form of String arrays, which you can use the Calendar fields to index in to. See How can I convert an Integer to localized month name in Java? for example.
Note you can use DateFormat.getDateInstance() to retrieve a pre-made format for the current locale (see the rest of those docs, there are also methods for getting pre-made time-only or date+time formats).
Basically you have the following options:
DateFormat (SimpleDateFormat for custom formats)
Locale-specific format (e.g. day/month/year ordering): Yes
Language-specific names (e.g. English "November" vs. Spanish "Noviembre"): Yes
Does the work for you: Yes. This is the best way and will provide a format that the user is used to working with, with no logic needed on your end.
printf date fields
Locale-specific format: No
Language-specific names: Yes
Does the work for you: Partly (up to you to determine field ordering)
Calendar fields with DateFormatSymbols
Locale-specific format: No
Language-specific names: Yes
Does the work for you: No
Calendar fields with your own string conversions (like a big switch statement):
Locale-specific format: No
Language-specific names: No
Does the work for you: No
Another advantage of DateFormat-based formats vs printf date fields is you can still define your own field ordering and formats with the SimpleDateFormat (just like printf) but you can stick to the DateFormat interface which makes it easier to pass around and combine with stock date formats like DateFormat.getDateInstance(DateFormat.MEDIUM).
Check out the documentation for DateFormat for info on the things you can do with it. Check out the documentation for SimpleDateFormat for info on creating custom date formats. Check out this nice example of date formats (archive) for some example output if you want instant gratification.
There's a direct way how to do it using printf, but it's a pain, too:
String.printf("Time: %1$td-%1$tm %1$tH:%1$tM", new Date());
One problem with it is that it uses 4 formatting strings with the same object, so it needs the 1$ prefix to always access the first argument. The other is that I can never remember what letter means what (but maybe that's just me).
Speed could actually be another problem, if you care.
This is documented in the underlying class Formatter.
My preffered way would be something like
myFormatter.format("Time: [d-m HH:MM]", new Date())
where the braces would save us from repeating $1 and make clear where the argument ends.

can we get the pattern of the given date object

How to get the pattern of the given date object
I am getting one Date object as a parameter in my method and I want to know the pattern of the date to convert it into user selected timezone.
You've misunderstood what a Date means. It's just a number of milliseconds since the Unix epoch. It has no concept of time zone, calendar or text format. If it helps, think of it as being a bit like int - an int isn't in hex, decimal or binary - it's just a number within a certain range. If you parse "1a" as hex, that gives an indistinguishable result from parsing "26" as decimal. The same goes for Date.
Of course, this was already explained in comments to some extent, but your reply of:
ok, but while i getting the date object which already set a format i want to know that format.
... suggests you didn't really understood it. The concept of "which already set a format" makes no sense in the context of a Date.
If you need a particular format to be applied, you should pass the DateFormat along as well as the Date.
You can't from the date object itself however (depending on your exact requirements) you could use
DateFormat.getDateTimeInstance()
Which will return to you the default style and format for the locale however like I said that's dependant on your requirement...
The alternative is change your method signature to accept the format as well.
You should create DateFormat. Date knows nothing about TimeZone.
Date date = new Date();
DateFormat formatter = new SimpleDateFormat("dd MMM yyyy HH:mm:ss");
// Set TimeZone
formatter.setTimeZone(TimeZone.getTimeZone("EST"));
System.out.println(formatter.format(date));
// Change timezone
formatter.setTimeZone(TimeZone.getTimeZone("IST"));
System.out.println(formatter.format(date));

How do I get localized date pattern string?

It is quite easy to format and parse Java Date (or Calendar) classes using instances of DateFormat.
I could format the current date into a short localized date like this:
DateFormat formatter = DateFormat.getDateInstance(DateFormat.SHORT, Locale.getDefault());
String today = formatter.format(new Date());
My problem is that I need to obtain this localized pattern string (something like "MM/dd/yy").
This should be a trivial task, but I just couldn't find the provider.
For SimpleDateFormat, You call toLocalizedPattern()
EDIT:
For Java 8 users:
The Java 8 Date Time API is similar to Joda-time. To gain a localized pattern we can use class
DateTimeFormatter
DateTimeFormatter.ofLocalizedDate(FormatStyle.MEDIUM);
Note that when you call toString() on LocalDate, you will get date in format ISO-8601
Note that Date Time API in Java 8 is inspired by Joda Time and most solution can be based on questions related to time.
For those still using Java 7 and older:
You can use something like this:
DateFormat formatter = DateFormat.getDateInstance(DateFormat.SHORT, Locale.getDefault());
String pattern = ((SimpleDateFormat)formatter).toPattern();
String localPattern = ((SimpleDateFormat)formatter).toLocalizedPattern();
Since the DateFormat returned From getDateInstance() is instance of SimpleDateFormat.
Those two methods should really be in the DateFormat too for this to be less hacky, but they currently are not.
It may be strange, that I am answering my own question, but I believe, I can add something to the picture.
ICU implementation
Obviously, Java 8 gives you a lot, but there is also something else: ICU4J. This is actually the source of Java original implementation of things like Calendar, DateFormat and SimpleDateFormat, to name a few.
Therefore, it should not be a surprise that ICU's SimpleDateFormat also contains methods like toPattern() or toLocalizedPattern(). You can see them in action here:
DateFormat fmt = DateFormat.getPatternInstance(
DateFormat.YEAR_MONTH,
Locale.forLanguageTag("pl-PL"));
if (fmt instanceof SimpleDateFormat) {
SimpleDateFormat sfmt = (SimpleDateFormat) fmt;
String pattern = sfmt.toPattern();
String localizedPattern = sfmt.toLocalizedPattern();
System.out.println(pattern);
System.out.println(localizedPattern);
}
ICU enhancements
This is nothing new, but what I really wanted to point out is this:
DateFormat.getPatternInstance(String pattern, Locale locale);
This is a method that can return a whole bunch of locale specific patterns, such as:
ABBR_QUARTER
QUARTER
YEAR
YEAR_ABBR_QUARTER
YEAR_QUARTER
YEAR_ABBR_MONTH
YEAR_MONTH
YEAR_NUM_MONTH
YEAR_ABBR_MONTH_DAY
YEAR_NUM_MONTH_DAY
YEAR_MONTH_DAY
YEAR_ABBR_MONTH_WEEKDAY_DAY
YEAR_MONTH_WEEKDAY_DAY
YEAR_NUM_MONTH_WEEKDAY_DAY
ABBR_MONTH
MONTH
NUM_MONTH
ABBR_STANDALONE_MONTH
STANDALONE_MONTH
ABBR_MONTH_DAY
MONTH_DAY
NUM_MONTH_DAY
ABBR_MONTH_WEEKDAY_DAY
MONTH_WEEKDAY_DAY
NUM_MONTH_WEEKDAY_DAY
DAY
ABBR_WEEKDAY
WEEKDAY
HOUR
HOUR24
HOUR_MINUTE
HOUR_MINUTE_SECOND
HOUR24_MINUTE
HOUR24_MINUTE_SECOND
HOUR_TZ
HOUR_GENERIC_TZ
HOUR_MINUTE_TZ
HOUR_MINUTE_GENERIC_TZ
MINUTE
MINUTE_SECOND
SECOND
ABBR_UTC_TZ
ABBR_SPECIFIC_TZ
SPECIFIC_TZ
ABBR_GENERIC_TZ
GENERIC_TZ
LOCATION_TZ
Sure, there are quite a few. What is good about them, is that these patterns are actually strings (as in java.lang.String), that is if you use English pattern "MM/d", you'll get locale-specific pattern in return. It might be useful in some corner cases. Usually you would just use DateFormat instance, and won't care about the pattern itself.
Locale-specific pattern vs. localized pattern
The question intention was to get localized, and not the locale-specific pattern. What's the difference?
In theory, toPattern() will give you locale-specific pattern (depending on Locale you used to instantiate (Simple)DateFormat). That is, no matter what target language/country you put, you'll get the pattern composed of symbols like y, M, d, h, H, M, etc.
On the other hand, toLocalizedPattern() should return localized pattern, that is something that is suitable for end users to read and understand. For instance, German middle (default) date pattern would be:
toPattern(): dd.MM.yyyy
toLocalizedPattern(): tt.MM.jjjj (day = Tag, month = Monat, year = Jahr)
The intention of the question was: "how to find the localized pattern that could serve as hint as to what the date/time format is". That is, say we have a date field that user can fill-out using the locale-specific pattern, but I want to display a format hint in the localized form.
Sadly, so far there is no good solution. The ICU I mentioned earlier in this post, partially works. That's because, the data that ICU uses come from CLDR, which is unfortunately partially translated/partially correct. In case of my mother's tongue, at the time of writing, neither patterns, nor their localized forms are correctly translated. And every time I correct them, I got outvoted by other people, who do not necessary live in Poland, nor speak Polish language...
The moral of this story: do not fully rely on CLDR. You still need to have local auditors/linguistic reviewers.
You can use DateTimeFormatterBuilder in Java 8. Following example returns localized date only pattern e.g. "d.M.yyyy".
String datePattern = DateTimeFormatterBuilder.getLocalizedDateTimePattern(
FormatStyle.SHORT, null, IsoChronology.INSTANCE,
Locale.GERMANY); // or whatever Locale
The following code will give you the pattern for the locale:
final String pattern1 = ((SimpleDateFormat) DateFormat.getDateInstance(DateFormat.SHORT, locale)).toPattern();
System.out.println(pattern1);
Java 8 provides some useful features out of the box for working with and formatting/parsing date and time, including handling locales. Here is a brief introduction.
Basic Patterns
In the simplest case to format/parse a date you would use the following code with a String pattern:
DateTimeFormatter.ofPattern("MM/dd/yyyy")
The standard is then to use this with the date object directly for formatting:
return LocalDate.now().format(DateTimeFormatter.ofPattern("MM/dd/yyyy"));
And then using the factory pattern to parse a date:
return LocalDate.parse(dateString, DateTimeFormatter.ofPattern("MM/dd/yyyy"));
The pattern itself has a large number of options that will cover the majority of usecases, a full rundown can be found at the javadoc location here.
Locales
Inclusion of a Locale is fairly simple, for the default locale you have the following options that can then be applied to the format/parse options demonstrated above:
DateTimeFormatter.ofLocalizedDate(dateStyle);
The 'dateStyle' above is a FormatStyle option Enum to represent the full, long, medium and short versions of the localized Date when working with the DateTimeFormatter. Using FormatStyle you also have the following options:
DateTimeFormatter.ofLocalizedTime(timeStyle);
DateTimeFormatter.ofLocalizedDateTime(dateTimeStyle);
DateTimeFormatter.ofLocalizedDateTime(dateTimeStyle, timeStyle);
The last option allows you to specify a different FormatStyle for the date and the time. If you are not working with the default Locale the return of each of the Localized methods can be adjusted using the .withLocale option e.g
DateTimeFormatter.ofLocalizedTime(timeStyle).withLocale(Locale.ENGLISH);
Alternatively the ofPattern has an overloaded version to specify the locale too
DateTimeFormatter.ofPattern("MM/dd/yyyy",Locale.ENGLISH);
I Need More!
DateTimeFormatter will meet the majority of use cases, however it is built on the DateTimeFormatterBuilder which provides a massive range of options to the user of the builder. Use DateTimeFormatter to start with and if you need these extensive formatting features fall back to the builder.
Please find in the below code which accepts the locale instance and returns the locale specific data format/pattern.
public static String getLocaleDatePattern(Locale locale) {
// Validating if Locale instance is null
if (locale == null || locale.getLanguage() == null) {
return "MM/dd/yyyy";
}
// Fetching the locale specific date pattern
String localeDatePattern = ((SimpleDateFormat) DateFormat.getDateInstance(
DateFormat.SHORT, locale)).toPattern();
// Validating if locale type is having language code for Chinese and country
// code for (Hong Kong) with Date Format as - yy'?'M'?'d'?'
if (locale.toString().equalsIgnoreCase("zh_hk")) {
// Expected application Date Format for Chinese (Hong Kong) locale type
return "yyyy'MM'dd";
}
// Replacing all d|m|y OR Gy with dd|MM|yyyy as per the locale date pattern
localeDatePattern = localeDatePattern.replaceAll("d{1,2}", "dd").replaceAll(
"M{1,2}", "MM").replaceAll("y{1,4}|Gy", "yyyy");
// Replacing all blank spaces in the locale date pattern
localeDatePattern = localeDatePattern.replace(" ", "");
// Validating the date pattern length to remove any extract characters
if (localeDatePattern.length() > 10) {
// Keeping the standard length as expected by the application
localeDatePattern = localeDatePattern.substring(0, 10);
}
return localeDatePattern;
}
Since it's just the locale information you're after, I think what you'll have to do is locate the file which the JVM (OpenJDK or Harmony) actually uses as input to the whole Locale thing and figure out how to parse it. Or just use another source on the web (surely there's a list somewhere). That'll save those poor translators.
You can try something like :
LocalDate fromCustomPattern = LocalDate.parse("20.01.2014", DateTimeFormatter.ofPattern("MM/dd/yy"))
Im not sure about what you want, but...
SimpleDateFormat example:
SimpleDateFormat sdf = new SimpleDateFormat("MM/dd/yy");
Date date = sdf.parse("12/31/10");
String str = sdf.format(new Date());

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