Develop Reference

java.time.LocalDate allow invalid value in date [duplicate]

I wanted to validate date in client side so I wrote the following code. But instead of getting an exception I am getting a proper date object for 31st of February date string, which is clearly an invalid date.
public class Test {
public static void main(String[] args) {
String dateFormat = "HH:mm:ss MM/dd/yyyy";
String dateString = "11:30:59 02/31/2015";
DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern(dateFormat, Locale.US);
try {
LocalDateTime date = LocalDateTime.parse(dateString, dateTimeFormatter);
System.out.println(date);
} catch (Exception e) {
// Throw invalid date message
}
}
}
Output : 2015-02-28T11:30:59
Does anyone know why LocalDateTime is parsing this date instead of throwing an exception.

You just need a strict ResolverStyle.
Parsing a text string occurs in two phases. Phase 1 is a basic text parse according to the fields added to the builder. Phase 2 resolves the parsed field-value pairs into date and/or time objects. This style is used to control how phase 2, resolving, happens.
Sample code - where withResolverStyle(ResolverStyle.STRICT) is the important change, along with the use of uuuu rather than yyyy (where uuuu is "year" and "yyyy" is "year of era", and therefore ambiguous):
import java.time.*;
import java.time.format.*;
import java.util.*;
public class Test {
public static void main(String[] args) {
String dateFormat = "HH:mm:ss MM/dd/uuuu";
String dateString = "11:30:59 02/31/2015";
DateTimeFormatter dateTimeFormatter = DateTimeFormatter
.ofPattern(dateFormat, Locale.US)
.withResolverStyle(ResolverStyle.STRICT);
try {
LocalDateTime date = LocalDateTime.parse(dateString, dateTimeFormatter);
System.out.println(date);
} catch (DateTimeParseException e) {
// Throw invalid date message
System.out.println("Exception was thrown");
}
}
}

The Java 8 DateTimeFormatter uses yyyy to mean YEAR_OF_ERA, and uuuu to mean YEAR. You need to modify your pattern string as follows:
String dateFormat = "HH:mm:ss MM/dd/uuuu";
The DateTimeFormatter defaults to using the SMART resolver style, but you want it to use the STRICT resolver style. Modify your dateTimeFormatter initialization code as follows:
DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern(dateFormat, Locale.US)
.withResolverStyle(ResolverStyle.STRICT);

It is not rounding down. February has never had 31 days, and it is impossible to use a validating date / time object to represent a day that doesn't exist.
As a result, it takes the invalid input and gives you the best approximation to the correct date (the last date of February that year).
SimpleDateFormat inherits from DateFormat which has a setLenient(boolean value) method on it. I would expect that if you called setLenient(true) prior to parsing, it would probably complain more, as detailed in the javadocs.

try {
SimpleDateFormat df = new java.text.SimpleDateFormat("HH:mm:ss MM/dd/yyyy");
df.setLenient(false);
System.out.println(df.parse("11:30:59 02/29/2015"));
} catch (java.text.ParseException e) {
System.out.println(e);
}
I found one solution to recognize date as a valid date with DateFormat.setLenient(boolean). If you try to parse any invalid date it will throws parse exception.
Edit:
Java 8, but this will raise exception if a month is not between 1 and 12, if a day is more than 32. Exactly not working. But for month its working.
try {
TemporalAccessor ta = DateTimeFormatter.ofPattern("HH:mm:ss MM/dd/yyyy").parse("11:30:59 02/32/2015");
} catch (Exception e) {
System.out.println(e);
}
Output:
java.time.format.DateTimeParseException: Text '11:30:59 02/32/2015' could not be
parsed: Invalid value for DayOfMonth (valid values 1 - 28/31): 32

LocalDateTime.parse will only throw an error if the String passed in contains invalid characters, a number of days exceeding 31 or a month exceeding 12.
For example, if you modified your code as such:
String dateString = "11:30:59 0zz2/31/2015";
an exception would be thrown caused by the invalid 'zz' characters within your given date. As to why it's 'rounding-down' the date so to speak, that I don't know.
Source: https://docs.oracle.com/javase/8/docs/api/java/time/LocalDateTime.html#parse-java.lang.CharSequence-

How do I ignore the time zone when parsing with Joda's DateTimeFormatter?

I'm trying to parse rubbish date values out of IPTC metadata. The format is supposed to be yyyyMMdd but in some situations it isn't. A particular value I have found is "Tue Jan 05 00:00:00 AEDT 2016".
If I try to parse this using Joda's DateTimeFormatter:
DateTimeFormat.forPattern("EEE MMM dd HH:mm:ss Z yyyy")
.parseLocalDate("Tue Jan 05 00:00:00 AEDT 2016");
This gives me an error:
java.lang.IllegalArgumentException: Invalid format: "Tue Jan 05 00:00:00 AEDT 2016" is malformed at "AEDT 2016"
I have tried the following zone symbols:
z
zz
Z
ZZ
ZZZ
I realise that the docs do say that DateTimeFormatter can't parse time zones. I also realise that these short time zone names are ambiguous. But in this situation I'm only trying to get out a LocalDate, so all I really want is the month, day and year. (Notice how the hour, minute and second are also zero?)
I would rather not have to regex crap out of the middle of the string before passing it off if possible, because the thing I'm passing this formatter off to expects a DateTimeFormatter at present.
Is there a way to specify some kind of arbitrary pattern of junk to throw away when parsing? I can't seem to find it in the API, but that doesn't necessarily mean it isn't there.

I'll post my own message workaround in the meantime, which uses a mix of existing format patterns plus a custom parser to throw away the time zone.
DateTimeFormatter formatter = new DateTimeFormatterBuilder()
.appendPattern("EEE MMM dd HH:mm:ss ")
.append(DateTimeFormat.forPattern("Z").getPrinter(), new DiscardTimeZoneSymbolParser())
.appendPattern(" yyyy")
.toFormatter();
LocalDate localDate = formatter.parseLocalDate("Tue Jan 05 00:00:00 AEDT 2016");
And then:
public class DiscardTimeZoneSymbolParser implements DateTimeParser {
#Override
public int estimateParsedLength() {
return 4;
}
#Override
public int parseInto(DateTimeParserBucket bucket, #NonNls String text, int position) {
for (int positionFromStart = 0; positionFromStart < 4; positionFromStart++, position++) {
boolean match;
if (position >= text.length()) {
match = false;
} else {
#NonNls
char ch = text.charAt(position);
match = ch >= 'A' && ch <= 'Z';
}
if (!match) {
if (positionFromStart >= 3) { // require 3 characters
return position;
} else {
return ~position;
}
}
}
return position;
}
}

You can use the parsing facilities in java.text:
DateFormat df = new SimpleDateFormat("EEE MMM dd HH:mm:ss Z yyyy", Locale.ENGLISH);
df.setLenient(false);
Date date = df.parse("Tue Jan 05 00:00:00 AEDT 2016");
and then transform the java.util.Date in the Joda LocalDate. Note that:
neither Date nor LocalDate have a timezone: Date is UTC, and LocalDate refers to a Chronology, not to an instant
I specified the Locale for the parser, but you may need to use the default locale of the JMV, or any other locale depending on your input

So the problem is the huge interface of DateTimeFormatter which prevents you writing your own implementation or decorator easily.
...the thing I'm passing this formatter off to expects a DateTimeFormatter at present.
Is it out of the question to refactor the framework (the "thing") like so:
Step 1: Create a new interface:
public interface LocalDateTimeParser {
LocalDate parseLocalDate(String text);
}
Step 2: Create an adaptor:
public final class DateTimeFormatterAdapter implements LocalDateTimeParser {
private final DateTimeFormatter adaptee;
public DateTimeFormatterAdapter(DateTimeFormatter adaptee){
this.adaptee = adaptee;
}
public LocalDate parseLocalDate(String text){
return adaptee.parseLocalDate(text);
}
}
Step 2: Reference LocalDateTimeParser in your framework where only local parsing is required and wrap the existing DateTimeFormatter in an adapter.
Step 3: Now you are free to write your own LocalDateTimeParser implementation with regex pre processing to strip the timezone and pass the rest to a DateTimeFormatter.

Java 8 LocalDateTime is parsing invalid date

I wanted to validate date in client side so I wrote the following code. But instead of getting an exception I am getting a proper date object for 31st of February date string, which is clearly an invalid date.
public class Test {
public static void main(String[] args) {
String dateFormat = "HH:mm:ss MM/dd/yyyy";
String dateString = "11:30:59 02/31/2015";
DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern(dateFormat, Locale.US);
try {
LocalDateTime date = LocalDateTime.parse(dateString, dateTimeFormatter);
System.out.println(date);
} catch (Exception e) {
// Throw invalid date message
}
}
}
Output : 2015-02-28T11:30:59
Does anyone know why LocalDateTime is parsing this date instead of throwing an exception.

You just need a strict ResolverStyle.
Parsing a text string occurs in two phases. Phase 1 is a basic text parse according to the fields added to the builder. Phase 2 resolves the parsed field-value pairs into date and/or time objects. This style is used to control how phase 2, resolving, happens.
Sample code - where withResolverStyle(ResolverStyle.STRICT) is the important change, along with the use of uuuu rather than yyyy (where uuuu is "year" and "yyyy" is "year of era", and therefore ambiguous):
import java.time.*;
import java.time.format.*;
import java.util.*;
public class Test {
public static void main(String[] args) {
String dateFormat = "HH:mm:ss MM/dd/uuuu";
String dateString = "11:30:59 02/31/2015";
DateTimeFormatter dateTimeFormatter = DateTimeFormatter
.ofPattern(dateFormat, Locale.US)
.withResolverStyle(ResolverStyle.STRICT);
try {
LocalDateTime date = LocalDateTime.parse(dateString, dateTimeFormatter);
System.out.println(date);
} catch (DateTimeParseException e) {
// Throw invalid date message
System.out.println("Exception was thrown");
}
}
}

The Java 8 DateTimeFormatter uses yyyy to mean YEAR_OF_ERA, and uuuu to mean YEAR. You need to modify your pattern string as follows:
String dateFormat = "HH:mm:ss MM/dd/uuuu";
The DateTimeFormatter defaults to using the SMART resolver style, but you want it to use the STRICT resolver style. Modify your dateTimeFormatter initialization code as follows:
DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern(dateFormat, Locale.US)
.withResolverStyle(ResolverStyle.STRICT);

It is not rounding down. February has never had 31 days, and it is impossible to use a validating date / time object to represent a day that doesn't exist.
As a result, it takes the invalid input and gives you the best approximation to the correct date (the last date of February that year).
SimpleDateFormat inherits from DateFormat which has a setLenient(boolean value) method on it. I would expect that if you called setLenient(true) prior to parsing, it would probably complain more, as detailed in the javadocs.

try {
SimpleDateFormat df = new java.text.SimpleDateFormat("HH:mm:ss MM/dd/yyyy");
df.setLenient(false);
System.out.println(df.parse("11:30:59 02/29/2015"));
} catch (java.text.ParseException e) {
System.out.println(e);
}
I found one solution to recognize date as a valid date with DateFormat.setLenient(boolean). If you try to parse any invalid date it will throws parse exception.
Edit:
Java 8, but this will raise exception if a month is not between 1 and 12, if a day is more than 32. Exactly not working. But for month its working.
try {
TemporalAccessor ta = DateTimeFormatter.ofPattern("HH:mm:ss MM/dd/yyyy").parse("11:30:59 02/32/2015");
} catch (Exception e) {
System.out.println(e);
}
Output:
java.time.format.DateTimeParseException: Text '11:30:59 02/32/2015' could not be
parsed: Invalid value for DayOfMonth (valid values 1 - 28/31): 32

LocalDateTime.parse will only throw an error if the String passed in contains invalid characters, a number of days exceeding 31 or a month exceeding 12.
For example, if you modified your code as such:
String dateString = "11:30:59 0zz2/31/2015";
an exception would be thrown caused by the invalid 'zz' characters within your given date. As to why it's 'rounding-down' the date so to speak, that I don't know.
Source: https://docs.oracle.com/javase/8/docs/api/java/time/LocalDateTime.html#parse-java.lang.CharSequence-

How to create a generic date formatter in java for Solr?

I've a requirement where date can be passed in the following formats before indexing them to Solr. Here are the examples of dates being passed
String dateStr = "2012-05-23T00:00:00-0400";
String dateStr1 = "May 24, 2012 04:57:40 GMT";
String dateStr2 = "2011-06-21";
The standard Solr format is "yyyy-MM-dd'T'HH:mm:ss'Z'".
I've tried SimpleDateFormat but is not able to write a generic program to support various formats. It ends up throwing parse exceptions.
I also tried joda time, but not been succeful so far in UTC conversion.
public static String toUtcDate(final String iso8601) {
DateTime dt = ISO_PARSE_FORMAT.parseDateTime(iso8601);
DateTime utcDt = dt.withZone(ZONE_UTC);
return utcDt.toString(ISO_PRINT_FORMAT);
}
Is there a standard library to achieve this ?
Any pointers will be appreciated.
Thanks

I just try the various formats until I get a hit:
public static String toUtcDate(String dateStr) {
SimpleDateFormat out = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'");
// Add other parsing formats to try as you like:
String[] dateFormats = {"yyyy-MM-dd", "MMM dd, yyyy hh:mm:ss Z"};
for (String dateFormat : dateFormats) {
try {
return out.format(new SimpleDateFormat(dateFormat).parse(dateStr));
} catch (ParseException ignore) { }
}
throw new IllegalArgumentException("Invalid date: " + dateStr);
}
I'm not aware of a library that does this.

Here is the answer:
Converting ISO 8601-compliant String to java.util.Date
Once you have your Date, you know how to get your UTC time.
Edit:
The accepted answer doesn't use joda time but jaxb.
By the way, where do these formats come from?
String dateStr = "2012-05-23T00:00:00-0400";
String dateStr1 = "May 24, 2012 04:57:40 GMT";
String dateStr2 = "2011-06-21";
If they are different from a locale to another, it may be possible they were generated by DateFormat.getDateTimeInstance(...,...) so perhaps try to figure out which has been used.

Java date format real simple

how would you write te date if i have a date and all i want is the month and the day like this (mm/dd) and then turn the month like this July, 08

Let me see if I understood well.
You have a date like "07/08" and you want "July, 08"?
You could try SimpleDateFormat
import java.text.SimpleDateFormat;
import java.text.ParseException;
class Test {
public static void main( String [] args ) throws ParseException {
SimpleDateFormat in = new SimpleDateFormat("MM/dd");
SimpleDateFormat out = new SimpleDateFormat("MMMM, dd");
System.out.println( out.format( in.parse("07/08") ) );
// Verbose
//String input = "07/09";
//Date date = in.parse( input );
//String output = out.format( date );
//System.out.println( output );
}
}

Use:
Format formatter = new SimpleDateFormat("MMMM, dd");
String s = formatter.format(date);
Formatting a Date Using a Custom Format

The SimpleDateFormat is your friend here. If you already have a java.util.Date object, just format it using the desired pattern (refer to the javadoc for details on date and time patterns):
SimpleDateFormat out = new SimpleDateFormat("MMMM, dd");
String s = out.format(date); // date is your existing Date object here
(EDIT: I'm adding some details as the original question is unclear and I may have missed the real goal.
If you have a String representation of a date in a given format (e.g. MM/dd) and want to transform the representation, you'll need 2 SimpleDateFormat as pointed out by others: one to parse the String into a Date and another one to format the Date.
SimpleDateFormat in = new SimpleDateFormat("MM/dd");
Date date = in.parse(dateAsString); // dateAsString is your String representation here
Then use the code snippet seen above to format it.)

the month and the day like this (mm/dd) and then turn the month like this July, 08
So you want to convert MM/dd to MMMM, dd? So you start with a String and you end up with a String? Then you need another SimpleDateFormat instance with the first pattern.
String dateString1 = "07/08";
Date date = new SimpleDateFormat("MM/dd").parse(dateString1);
String dateString2 = new SimpleDateFormat("MMMM, dd").format(date);
System.out.println(dateString2); // July, 08 (monthname depends on locale!).