Develop Reference

Date formatting in Java to a specific format

The date I fetched from an open API is 2021-04-28. I want to format it in this way: 4/28/2021. Below is the method I tried:
public String formatDateFetchedFromAPI(String transDate) {
LocalDate apiDate = LocalDate.parse(transDate, DateTimeFormatter.BASIC_ISO_DATE);
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("M/d/yyyy");
String actualDate = formatter.format(apiDate);
return actualDate;
}
This throws an error saying:
java.time.format.DateTimeParseException: Text '2021-04-28' could not be parsed at index 4
If the data that I pull from open API is 20210426 then this method works just fine and returns 4/28/2021.

Your date looks like an ISO_LOCAL_DATE and not BASIC_ISO_DATE, so instead you can just use
LocalDate apiDate = LocalDate.parse(transDate);
without DateTimeFormatter, because LocalDate.parse by default uses ISO_LOCAL_DATE.

LGoodDatePicker issues with getDate()

I'm using the LGoodDatePicker with Apache NetbeansIDE 12.2 (https://github.com/LGoodDatePicker/LGoodDatePicker), and I need to get the date in the format YYYY-MM-DD. I'm using this code:
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
String date = sdf.format(datePicker1.getDate());
But I get this error:
Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: Cannot format given Object as a Date
Any suggestions? Thank you.

The method getDate() of this DatePicker returns a java.time.LocalDate, not a java.util.Date. That's actually what the error message tells you, it expects a java.util.Date but got something else.
That means you shouldn't try to format it using a java.text.SimpleDateFormat, use a java.time.format.DateTimeFormatter here:
String date = datePicker1.getDate().format(DateTimeFormatter.ISO_LOCAL_DATE);
or define a custom pattern using the method ofPattern(String pattern) of the DateTimeFormatter:
String date = datePicker1.getDate().format(DateTimeFormatter.ofPattern("uuuu-MM-dd");
In this very case, you can even use the toString() method of the LocalDate in order to get a String in the desired format:
String date = datePicker1.getDate().toString();

Convert a string into iso date format

So I am trying to convert a string into an iso format for the date.
This is the string that I am trying to convert "2016-07-05 02:14:35.0"
I would like to have it in this format the iso 8601
"2016-07-05T02:14:35.0"
I have this so far
DateTimeFormatter format = DateTimeFormat.forPattern("YYYY-MM-DDTHH:mm:sszzz");
new LocalDate();
LocalDate newDate = LocalDate.parse(created,format);
created = newDate.toString();
But it is giving me this exception
ERROR: Illegal pattern component: T; nested exception is java.lang.IllegalArgumentException: Illegal pattern component: T
I followed the examples and I don't know what I am doing wrong here.
Any help would be appreciated.

Firstly, that value is a LocalDateTime, not a LocalDate. If you want to get a date out in the end, I'd convert it to a LocalDateTime first, then take the date part of that.
When performing date formatting and parsing, always read the documentation really carefully. It looks like you're using Joda Time (due to using forPattern; if you can move to Java 8 that would be beneficial). That means you should be reading the DateTimeFormat docs.
Current problems with your pattern:
You're using 'D' instead of 'd'; that means day-of-year
You've specified 'T' without quoting it, and it isn't in the pattern anyway
You've ignored the fraction-of-second part of your value
You've specified 'zz' when there's no time zone indicator in the value.
Here's a working example:
import org.joda.time.*;
import org.joda.time.format.*;
public class Test {
public static void main(String[] args) {
String text = "2016-07-05 02:14:35.0";
DateTimeFormatter format = DateTimeFormat.forPattern("yyyy-MM-dd HH:mm:ss.S");
LocalDateTime localDateTime = LocalDateTime.parse(text, format);
System.out.println(localDateTime);
}
}
If you actually want to parse values with T in the middle, you'd use a pattern of "yyyy-MM-dd'T'HH:mm:ss.S" - note how then the T is quoted so it's treated literally instead of as a format specifier.
Note that this is just parsing. It's not "converting a string into ISO date format" - it's converting a string into a LocalDateTime. If you then want to format that value in an ISO format, you need to be using DateTimeFormatter.print, with an appropriate format. For example, you might want to convert to a format of yyyy-MM-dd'T'HH:mm:ss.S':
import org.joda.time.*;
import org.joda.time.format.*;
public class Test {
public static void main(String[] args) {
String text = "2016-07-05 02:14:35.0";
DateTimeFormatter parser = DateTimeFormat.forPattern("yyyy-MM-dd HH:mm:ss.S");
LocalDateTime localDateTime = LocalDateTime.parse(text, parser);
DateTimeFormatter printer = DateTimeFormat.forPattern("yyyy-MM-dd'T'HH:mm:ss.S");
String formatted = printer.print(localDateTime);
System.out.println(formatted); // Output 2016-07-05T02:14:35.0
}
}
The code above will only handle a single digit fraction-of-second. You could parse using .SSS instead of .S, but you really need to work out what you want the output to be in different cases (e.g. for 100 milliseconds, do you want .1 or .100?).

You have some errors in your code:
The pattern should be 'yyyy-MM-dd HH:mm:ss.SSS'. Be aware of upper-
and lowercase.
Use LocalDateTime to get date and time. LocalDate only holds the date.
The corrected code:
String created = "2016-07-05 02:14:35.000";
DateTimeFormatter format = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS");
LocalDateTime newDate = LocalDateTime.parse(created,format);
created = newDate.toString();
System.out.println(created);

Use the following format to convert
String format = "yyyy-mm-dd hh:mm:ss"
You are using the wrong format to convert. Using T is only to separate the date from time.
Use the format like this
String = "yyyy-MM-dd'T'HH:mm:ss"

DateFormat from ''yyyy-MM-dd" to "dd-MM" using Joda-Time

I have following code:
DateTimeFormatter dtf = DateTimeFormat.forPattern("dd/MM");
LocalDate weekMon = new LocalDate().withWeekOfWeekyear(thisWeek).withDayOfWeek(DateTimeConstants.MONDAY);
System.out.println(weekMon.toString());
LocalDate weekFin = dtf.parseLocalDate(weekMon.toString());
and the output prints the date correctly: 2015-02-02. I'm trying to convert it to European format and ignoring the year as "dd-MM" -> "02-02" but the line:
LocalDate weekFin = dtf.parseLocalDate(weekMon.toString());
keeps throwing following exception:
java.lang.IllegalArgumentException: Invalid format: "2015-02-02" is malformed at "5-02-02"
What is wrong with the formation in this case ?.

Probably what you need is to print, and not to parse.
In other words:
String dateStr = dtf.print(weekMon);
Notice that with this code:
LocalDate weekFin = dtf.parseLocalDate(weekMon.toString());
you are trying to parse a string in "yyyy-MM-dd" format using a formatter that accepts strings in "dd/MM" format. Hence the exception...

Java util.numberFormatException for input string: "2014-01-12 05-44-56"

I'm new in OFBiz, and Java. I used bellow block of code for checking date time input and use that for searching in table.
Timestamp strtDate = UtilDateTime.getTimestamp((String)request.getParameter("strt_date"));
if(strtDate != null)
{
// then here i used the date for taking data.
}
When i fill the date time field of form to search or when no date is selected for searching error occure that show numberFormatException, so how i can solve that? thanks for any help and guide.

Based on the Apache ofbiz API it looks like UtilDateTime#getTimestamp(String) expects milliseconds value. You are passing in "2014-01-12 05-44-56". You need to parse your date first. With pure pre 1.8 java (keep in mind that formatters aren't thread safe):
String dateString = "2014-01-12 05-44-56";
SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH-mm-ss");
Date date = formatter.parse(dateString);
UtilDateTime.getTimestamp(date.getTime());
Since java 1.8 (highly recommended to switch if you can!):
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH-mm-ss");
ZonedDateTime date = ZonedDateTime.parse(text, formatter);
long millis = date.toInstant().toEpochMilli();

you have to pass time in milliseconds not as you are passing.
you can check code also :
public static Timestamp getTimestamp(String milliSecs) throws NumberFormatException {
return new Timestamp(Long.parseLong(milliSecs));
}
it will parse the data in long which you are passing and that should be valid long value.

request.getParameter("strt_date") will anyways return String, so no need to cast it explicitly to String. Moreover, there will be a contract between Client & Server on the required Date Format. So you have to parse the String-Date in the same format using SimpleDateFormat. Code outlook will look like bellow:
SimpleDateFormat formatter = new SimpleDateFormat("contract-date-format");
Date date = formatter.parse(request.getParameter("strt_date"));
UtilDateTime.getTimestamp(date.getTime());