Develop Reference

Display time without converting to local time zone

I have an API that gives me this JSON response
{
"time": "2020-05-25T05:18:02.279842+01:00",
"timezone_name": "LMT",
"timezone": "Europe/London"
}
Now, I have 2 problems.
Converting the time to date object. I used SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSSSSZ") but, gives me parse exception. I think it’s because of milliseconds which is in 6 digits SSSSSS(279842). So I converted this 2020-05-25T05:18:02.279842+01:00" to 2020-05-25T05:18:02.279+01:00" which worked. I’m not satisfied with string manipulation.
When I format the date from above, I see the time in my local time zone not the London time. I think I have to set the time zone for the date object which is given in the time zone.
Overall, I just want to neatly parse the txt to data object and show the time in given time zone.
Appreciate your inputs.

I ended up with this solution.
private fun format(str: String): String {
// expected input format "2020-05-24T08:19:40.807726-05:00"
try {
val slits = str.split(".")
val inputFormat = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss")
inputFormat.timeZone = TimeZone.getTimeZone(timezone/*"Europe/London"*/)
val outputFormat = SimpleDateFormat("h:mm a")
outputFormat.timeZone = inputFormat.timeZone
return outputFormat.format(inputFormat.parse(slits[0])!!)
} catch (e: Exception) {
Log.e(MWLocationInfo::class.java.simpleName, e.stackTrace.toString());
}
return "-"
}

About 2 - SimpleDateFormat always returns time in local time of JVM, so you need to set timezone to SimpleDateFormat as
TimeZone timeZone = TimeZone.getTimeZone("Europe/London");
simpleDateFormat.setTimeZone(timeZone);
SimpleDateFormat is now legacy, think of using java.time API (introduced in java 8). Using java.time API -
ZonedDateTime zonedDateTime = ZonedDateTime.parse("2020-05-25T05:18:02.279842+01:00[Europe/London]");

What is the Standard way to Parse different Dates passed as Query-Params to the REST API?

I am working on a REST API which supports Date as a query param. Since it is Query param it will be String. Now the Date can be sent in the following formats in the QueryParams:
yyyy-mm-dd[(T| )HH:MM:SS[.fff]][(+|-)NNNN]
It means following are valid dates:
2017-05-05 00:00:00.000+0000
2017-05-05 00:00:00.000
2017-05-05T00:00:00
2017-05-05+0000
2017-05-05
Now to parse all these different date-times i am using Java8 datetime api. The code is as shown below:
DateTimeFormatter formatter = new DateTimeFormatterBuilder().parseCaseInsensitive()
.append(DateTimeFormatter.ofPattern("yyyy-MM-dd[[ ][['T'][ ]HH:mm:ss[.SSS]][Z]"))
.toFormatter();
LocalDateTime localDateTime = null;
LocalDate localDate = null;
ZoneId zoneId = ZoneId.of(ZoneOffset.UTC.getId());
Date date = null;
try {
localDateTime = LocalDateTime.parse(datetime, formatter);
date = Date.from(localDateTime.atZone(zoneId).toInstant());
} catch (Exception exception) {
System.out.println("Inside Excpetion");
localDate = LocalDate.parse(datetime, formatter);
date = Date.from(localDate.atStartOfDay(zoneId).toInstant());
}
As can be seens from the code I am using DateTimeFormatter and appending a pattern. Now I am first trying to parse date as LocalDateTime in the try-block and if it throws an exception for cases like 2017-05-05 as no time is passed, I am using a LocalDate in the catch block.
The above approach is giving me the solution I am looking for but my questions are that is this the standard way to deal with date sent as String and is my approach is in line with those standards?
Also, If possible what is the other way I can parse the different kinds of date (shown as the Valid dates above) except some other straightforward solutions like using an Array list and putting all the possible formats and then using for-loop trying to parse the date?

DateTimeFormatter formatter = new DateTimeFormatterBuilder()
.append(DateTimeFormatter.ISO_LOCAL_DATE)
// time is optional
.optionalStart()
.parseCaseInsensitive()
.appendPattern("[ ]['T']")
.append(DateTimeFormatter.ISO_LOCAL_TIME)
.optionalEnd()
// offset is optional
.appendPattern("[xx]")
.parseDefaulting(ChronoField.HOUR_OF_DAY, 0)
.parseDefaulting(ChronoField.OFFSET_SECONDS, 0)
.toFormatter();
for (String queryParam : new String[] {
"2017-05-05 00:00:00.000+0000",
"2017-05-05 00:00:00.000",
"2017-05-05T00:00:00",
"2017-05-05+0000",
"2017-05-05",
"2017-05-05T11:20:30.643+0000",
"2017-05-05 16:25:09.897+0000",
"2017-05-05 22:13:55.996",
"2017-05-05t02:24:01"
}) {
Instant inst = OffsetDateTime.parse(queryParam, formatter).toInstant();
System.out.println(inst);
}
The output from this snippet is:
2017-05-05T00:00:00Z
2017-05-05T00:00:00Z
2017-05-05T00:00:00Z
2017-05-05T00:00:00Z
2017-05-05T00:00:00Z
2017-05-05T11:20:30.643Z
2017-05-05T16:25:09.897Z
2017-05-05T22:13:55.996Z
2017-05-05T02:24:01Z
The tricks I am using include:
Optional parts may be included in either optionalStart/optionalEnd or in [] in a pattern. I use both, each where I find it easier to read, and you may prefer differently.
There are already predefined formatters for date and time of day, so I reuse those. In particular I take advantage of the fact that DateTimeFormatter.ISO_LOCAL_TIME already handles optional seconds and fraction of second.
For parsing into an OffsetDateTime to work we need to supply default values for the parts that may be missing in the query parameter. parseDefaulting does this.
In your code you are converting to a Date. The java.util.Date class is long outdated and has a number of design problems, so avoid it if you can. Instant will do fine. If you do need a Date for a legacy API that you cannot change or don’t want to change just now, convert in the same way as you do in the question.
EDIT: Now defaulting HOUR_OF_DAY, not MILLI_OF_DAY. The latter caused a conflict when only the millis were missing, but it seems the formatter is happy with just default hour of day when the time is missing.

I usually use the DateUtils.parseDate which belongs to commons-lang.
This method looks like this:
public static Date parseDate(String str,
String... parsePatterns)
throws ParseException
Here is the description:
Parses a string representing a date by trying a variety of different parsers.
The parse will try each parse pattern in turn. A parse is only deemed successful if it parses the whole of the input string. If no parse patterns match, a ParseException is thrown.
The parser will be lenient toward the parsed date.

#Configuration
public class DateTimeConfig extends WebMvcConfigurationSupport {
/**
* https://docs.spring.io/spring-framework/docs/current/reference/html/core.html#format-configuring-formatting-globaldatetimeformat
* #return
*/
#Bean
#Override
public FormattingConversionService mvcConversionService() {
DefaultFormattingConversionService conversionService = new DefaultFormattingConversionService(false);
conversionService.addFormatterForFieldAnnotation(new NumberFormatAnnotationFormatterFactory());
// Register JSR-310 date conversion with a specific global format
DateTimeFormatterRegistrar dateTimeRegistrar = new DateTimeFormatterRegistrar();
dateTimeRegistrar.setDateTimeFormatter(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));
dateTimeRegistrar.setDateTimeFormatter(DateTimeFormatter.ofPattern("yyyy-MM-dd"));
dateTimeRegistrar.setDateTimeFormatter(DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss'Z'"));
dateTimeRegistrar.registerFormatters(conversionService);
// Register date conversion with a specific global format
DateFormatterRegistrar dateRegistrar = new DateFormatterRegistrar();
dateRegistrar.setFormatter(new DateFormatter("yyyy-MM-dd"));
dateRegistrar.setFormatter(new DateFormatter("yyyy-MM-dd HH:mm:ss"));
dateRegistrar.setFormatter(new DateFormatter("yyyy-MM-dd'T'HH:mm:ss'Z'"));
dateRegistrar.registerFormatters(conversionService);
return conversionService;
}
}

Generating all days between 2 given dates in Java [duplicate]

This question already has answers here:
how to get a list of dates between two dates in java
(23 answers)
Closed 6 years ago.
I'm trying to get an array of Dates, while my input is a 'from'/'to' structure.
So my input is:
String date1 = "2014-01-01";
String date2 = "2014-05-01";
My output should be an Arraylist with all dates between date1 and date2.
I've already looked for this, but I could only find questions about the difference between 2 dates:
SimpleDateFormat myFormat = new SimpleDateFormat("dd MM yyyy");
String inputString1 = "23 01 1997";
String inputString2 = "27 04 1997";
try {
Date date1 = myFormat.parse(inputString1);
Date date2 = myFormat.parse(inputString2);
long diff = date2.getTime() - date1.getTime();
System.out.println ("Days: " + TimeUnit.DAYS.convert(diff,TimeUnit.MILLISECONDS));
} catch (ParseException e) {
e.printStackTrace();
}
Any hints or suggestions? All other questions are for iOS or SQL.

Take a look at JodaTime: http://joda-time.sourceforge.net/apidocs/org/joda/time/DateTime.html
DateTime dateTime1 = new DateTime(date1);
DateTime dateTime2 = new DateTime(date2);
List<Date> allDates = new ArrayList();
while( dateTime1.before(dateTime2) ){
allDates.add( dateTime1.toDate() );
dateTime1 = dateTime1.plusDays(1);
}

Below is the code to get array of dates between the two string date.
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.List;
public class DateFormatExample {
public static void main(String[] args) {
// TODO Auto-generated method stub
SimpleDateFormat myFormat = new SimpleDateFormat("yyyy-MM-dd");
SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");
String date1 = "2014-01-01";
String date2 = "2014-05-01";
try {
Date d1 = myFormat.parse(date1);
Date d2 = myFormat.parse(date2);
List<Date> allDates = new ArrayList<Date>();
List<String> allDatesString = new ArrayList<String>();
while( d1.before(d2) ){
d1 = addDays(d1, 1);
allDates.add(d1);
allDatesString.add(formatter.format(d1));
}
System.out.println(allDates);
System.out.println(allDatesString);
} catch (ParseException e) {
e.printStackTrace();
}
}
private static Date addDays(Date d1, int i) {
GregorianCalendar cal = new GregorianCalendar();
cal.setTime(d1);
cal.add(Calendar.DATE, 1);
return cal.getTime();
}
}

If you don't want to use third party libraries you can use Calendar:
Check here a working demo.
public static void main(String[] args) throws Exception {
SimpleDateFormat myFormat = new SimpleDateFormat("dd MM yyyy");
String inputString1 = "23 01 1997";
String inputString2 = "27 04 1997";
ArrayList<Date> dates = new ArrayList<Date>();
try {
Date date1 = myFormat.parse(inputString1);
Calendar c1 = DateToCalendar(date1);
Date date2 = myFormat.parse(inputString2);
Calendar c2 = DateToCalendar(date2);
while (!areEqualDate(c1, c2)) {
dates.add(c1.getTime());
System.out.println (c1.getTime());
c1.add(Calendar.DAY_OF_YEAR, 1);
}
} catch (ParseException e) {
e.printStackTrace();
}
// ArrayList<Date> dates >> contain all dates between both given days.
}
private static boolean areEqualDate(Calendar c1, Calendar c2) {
if (c1.get(Calendar.YEAR) != c2.get(Calendar.YEAR)) return false;
if (c1.get(Calendar.MONTH) != c2.get(Calendar.MONTH)) return false;
if (c1.get(Calendar.DAY_OF_YEAR) != c2.get(Calendar.DAY_OF_YEAR)) return false;
return true;
}
public static Calendar DateToCalendar(Date date) {
Calendar cal = Calendar.getInstance();
cal.setTime(date);
return cal;
}

I like JodaTime, but this can also be done without 3rd party libraries by using java.util.Calendar. Given a Calendar object, one can use its add method to increase certain fields of the date while honoring the calendar rules (like adding 1 day to the 31st of January gets you to the 1st of February, not to the 32nd of January).
First get the dates into one Calendar object each, in the correct chronological order so adding is going in the right direction later:
Calendar cStart = Calendar.getInstance(),
cStop = Calendar.getInstance();
if (date1.before(date2)) {
cStart.setTime(date1);
cStop.setTime(date2);
} else {
cStart.setTime(date2);
cStop.setTime(date1);
date1 and date2 are the parsed Date objects from your question, for simplicity's sake.
Next, loop over an "add 1 to day-of-year" instruction until this gets you beyond the stop date:
do {
System.out.println(pretty(cStart));
cStart.add(Calendar.DAY_OF_YEAR, 1);
} while (cStart.before(cStop));
And lastly print the stop date
System.out.println(pretty(cStop));
pretty() is just some mini method sending the calendar through a SDF, like the one you used for parsing the Strings in the first place.
This solution will print the date range, including the start and stop dates, and might need some tweaking around the edge cases (like date1==date2). Can be easily adapted to exclude the start and stop dates. Printing can be swapped for aggregation of course. To get a Date object from the calendar, use the getTime() method (returns a snapshot, not a live reference).
The documentation for the relevant (Gregorian)Calendar can be found here.

In case you are using Guava, there is a very elegant solution to this problem.
Guava has two neat classes, such as Range and ContiguousSet, which implement exactly what you need: first one operates on ranges of values, and second one - is able to convert a range to a set of discrete values.
Example of usage of both (together with JodaTime):
LocalDate start = LocalDate.parse("2015-01-01");
LocalDate end = LocalDate.parse("2019-02-01");
Range<LocalDate> range = Range.closed(start, end); //Creates a "closed" range, that is both dates are inclusive. There are also options like "openClosed", "closedOpen" and "open"
final Set<LocalDate> daySet = ContiguousSet.create(range, LocalDateDomain.INSTANCE); //Create a "virtual" set of days in given the range. "virtual" part means that if you create a set of 10 thousand years, it will not eat your memory at all
for (LocalDate day : daySet) {
//...operation...
}
Personally, I really prefer this way, as it eliminates some problems with understanding closed/open ranges, and makes code much easier to read and understand, while making no impact on performance. Also, it works with any kinds of dates, any libraries (you can swap YodaTime to Java8 Dates or even Java7- Date-based implementation).
Moreover, it allows you to do some neat operations on ranges like intersections, unions, spanning of ranges, incredibly fast "contains" and so on.
Only downsides are:
Dependence on Guava.
Need to create a special "DiscreteDomain" class, which Guava uses to understand where one date ends and other begins.
Example of LocalDateDomain implementation which operates as a bridge between Guava and JodaTime:
public class LocalDateDomain extends DiscreteDomain<LocalDate> {
public static final LocalDateDomain INSTANCE = new LocalDateDomain();
#Override
public LocalDate next(LocalDate value) {
return value.plusDays(1);
}
#Override
public LocalDate previous(LocalDate value) {
return value.minusDays(1);
}
#Override
public long distance(LocalDate start, LocalDate end) {
return Days.daysBetween(start, end).getDays();
}
}

I already know that OP isn't using Java 8 but here's the current solution - Java has been revamped and the new java.time API does every conceivable job in that regard:
//change these values :
LocalDate ld1 = LocalDate.ofEpochDay(0);
LocalDate ld2 = LocalDate.now();
//do NOT change these:
final LocalDate begin = ld1.isBefore(ld2) ? ld1 : ld2;
final LocalDate end = ld2.isAfter(ld1) ? ld2 : ld1;
for (int i = 0; i < begin.until(end, ChronoUnit.DAYS); i++) {
final LocalDate curDate = begin.plusDays(i);
System.out.println("current date : " + curDate);
}
This will output every valid day between the two dates whereas most of the other solutions will also give you invalid ones; heres the thing: temporal calculations need to be done on timezone-independent data - the output on the other hand may very well be timezone and/or chronology -dependent.
Thats why there are packages like java.time.format - simply calculate your time/date values and format them for your chosen region ... thats how its done correctly.
If you need to convert temporal input there are also useful functions in the time-API, i recommend doing a thorough tutorial on the subject, a few good introductions may be this and especially that :
There are two basic ways to represent time. One way represents time in
human terms, referred to as human time, such as year, month, day,
hour, minute and second. The other way, machine time, measures time
continuously along a timeline from an origin, called the epoch, in
nanosecond resolution. The Date-Time package provides a rich array of
classes for representing date and time. Some classes in the Date-Time
API are intended to represent machine time, and others are more suited
to representing human time.

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());

How to get TimeZone id for specified ISO country code?

I have a requirement where I have to convert timezone from UTC to a specific timezone and vice-versa taking into account day light saving. I am using java.util.TimeZone class for it. Now, issue is that there are several hundred Ids for timezone which cannot be displayed to user.
As a work around now we have decided to have country list first and list time-zones for country selected. I am not able to get TimeZone for an ISO country code.
Here is code which I am currently using to convert timezones,
Timestamp convertedTime = null;
try{
System.out.println("timezone: "+timeZone +", timestamp: "+timeStamp);
Locale locale = Locale.ENGLISH;
TimeZone destTimeZone = TimeZone.getTimeZone(timeZone);// TimeZone.getDefault();
System.out.println("Source timezone: "+destTimeZone);
DateFormat formatter = DateFormat.getDateTimeInstance(
DateFormat.DEFAULT,
DateFormat.DEFAULT,
locale);
formatter.setTimeZone(destTimeZone);
Date date = new Date(timeStamp.getTime());
System.out.println(formatter.format(date));
convertedTime = new Timestamp(date.getTime());
/*long sixMonths = 150L * 24 * 3600 * 1000;
Date inSixMonths = new Date(timeStamp.getTime() + sixMonths);
System.out.println("After 6 months: "+formatter.format(inSixMonths));
I need to find out timezone Id to be used in above code for given country ISO code.
Update: tried many things and below code gets me to list of timezones with 148 entries (which is still large). Can any one please help me to shorten it. Or, suggest some other way to either have a shorten list of timezones or get timezones for a country,
Code:
public class TimeZones {
private static final String TIMEZONE_ID_PREFIXES =
"^(Africa|America|Asia|Atlantic|Australia|Europe|Indian|Pacific)/.*";
private List<TimeZone> timeZones = null;
public List<TimeZone> getTimeZones() {
if (timeZones == null) {
initTimeZones();
}
return timeZones;
}
private void initTimeZones() {
timeZones = new ArrayList<TimeZone>();
final String[] timeZoneIds = TimeZone.getAvailableIDs();
for (final String id : timeZoneIds) {
if (id.matches(TIMEZONE_ID_PREFIXES)) {
timeZones.add(TimeZone.getTimeZone(id));
}
}
Collections.sort(timeZones, new Comparator<TimeZone>() {
public int compare(final TimeZone a, final TimeZone b) {
return a.getID().compareTo(b.getID());
}
});
}

I think ICU4J package will help you.

You can shorten your list with hasSameRules()... this should reduce you selection to about 50:
iterate through -> file equal time zones -> choose the most recognizables
The country- list has to have about 200 entries with a whole lot of uninteresting ones such as Gibraltar or St Martin... don't like that idea

Was able to get things working. I have created own database table with all time-zones as appearing in windows OS and their corresponding TimeZone IDs. Conversion is done using java.util.TimeZone class.
Thanks Namal and Frank for your inputs.