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Change date from MM/dd to yyyy-MM-dd'T'HH:mm:ss.SSZ in Java

I have a String that formatted MM/dd. I would like to convert it to a Date in format yyyy-MM-dd'T'HH:mm:ss.SSZ.
DateFormat df = new SimpleDateFormat("MM/dd");
String strDate = "06/05";
Date date = new Date();
date = df.parse(strDate);
This makes it a Date, but in the original format.
System.out.println(new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSZ").format(date));
This returns the correct month and day, but nopthing else.
1970-06-05T00:00:00.00-0400
Any idea how I can make it return
CURRENT_YEAR-06-05TCURRENT_TIME

In the question, the date format pattern indicates a desire for 2-digit fractional seconds. SimpleDateFormat cannot do that.
The newer Java 8 Time API can, and you should be using that anyway.
If you're running on Java 6 or 7, get the ThreeTen-Backport library.
To parse a MM/dd formatted string and get a full timestamp with current year and time-of-day, in the default time zone, use the following code:
String strDate = "06/05";
MonthDay monthDay = MonthDay.parse(strDate, DateTimeFormatter.ofPattern("MM/dd"));
ZonedDateTime date = ZonedDateTime.now().with(monthDay);
System.out.println(date.format(DateTimeFormatter.ofPattern("uuuu-MM-dd'T'HH:mm:ss.SSZ")));
Sample Output
2020-06-05T14:52:48.45-0400

I recommend to make use of java.time package. There you go:
var ds = "01/12";
var df = java.time.format.DateTimeFormatter.ofPattern("MM/dd");
var dt = java.time.MonthDay.from(df.parse(ds)).adjustInto(java.time.LocalDateTime.now());
Then you can convert dt to java.util.Date or whatever you like. Or simply use one of java.time formaters to get the desired output.

You are creating a date with only month and day
If you want to use the current year and time, you can create a calendar object and edit the month and day

For something this simple I suggest a different approach, get current time then set month and day from the original string THEN format.
String str = "08/09";
String[] split = str.split("/");
Calendar calendar = Calendar.getInstance();
calendar.set(Calendar.MONTH, Integer.parseInt(split[0]));
calendar.set(Calendar.DAY_OF_MONTH, Integer.parseInt(split[1]));
System.out.println(new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS").format(calendar.getTime()));

String strDate = "06-05";
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-"+strDate+"'T'HH:mm:ss.SSZ");
System.out.println(sdf.format(new Date()));
the output:
2020-06-05T23:00:45.306+0400

How to delete some character from respone in Java?

I have some string respone date like this:
2018-11-30 12:00:00
and i want just get the time, so i want like this:
12.00
and my question, can we delete some character like that?

Sounds like you want to use SimpleDateFormat so something like:
Date today = Calendar.getInstance().getTime();
SimpleDateFormat formatter = new SimpleDateFormat("hh.mm");
String folderName = formatter.format(today);
Based on your comment try:
int index = time.indexOf(‘:’);
int start = index -2;
int end = index + 2;
String newTime = time.substring(start,end);

String apiDateString = "2018-11-30 12:00:00"; // in this case, your string from api
Date apiDate = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").parse(apiDateString); // convert api date string to date
SimpleDateFormat formatter = new SimpleDateFormat("hh.mm");
String yourDateString = formatter.format(apiDate);
I think you want this.
Edited with little comment.
convert string to date. (apiDateString to apiDate)
create new format for what you want to form. In this case, 12.00
convert apiDate to your format. (apiDate -> 12.00)

You can try this
Calendar calendar = Calendar.getInstance();
SimpleDateFormat mdformat = new SimpleDateFormat("HH:mm:ss");
String strDate = "Current Time : " + mdformat.format(calendar.getTime());
display(strDate);

You can use SimpleDateFormat to get time and then replace : by .
I hope it can help your problem!

You can refer to this post.
Use SimpleDateFormat to format you date.
From String to Date
// Convert from string to date
String yourDate = "2018-11-30 12:00:00";
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Date date = format.parse(yourDate);
//Use calender instead of date to getHours and minute, due to deprecated
Calendar calendar = GregorianCalendar.getInstance();
calendar.setTime(date);
calendar.get(Calendar.HOUR);
calendar.get(Calendar.MINUTE);
System.out.println(calendar.get(Calendar.HOUR_OF_DAY)+"."+calendar.get(Calendar.MINUTE)); //12.0

Subtract char of digits like normal integers

I have two strings which can be seen as time stamps:
String min="2017-04-15 13:27:31";
String max="2017-04-15 13:40:01";
Assume we want to find out the time passed from first time stamp to the second one. If there was only the time and no date included, I could get it using my following code:
String[] partsMin=min.split(":");
String[] partMax=max.split(":");
int diffZero=Integer.parseInt(partMax[0])-Integer.parseInt(partsMin[0]);
int diffOne=Integer.parseInt(partMax[1])-Integer.parseInt(partsMin[1]);
int diffOTwo=Integer.parseInt(partMax[2])-Integer.parseInt(partsMin[2]);
diffInSec=diffZero*3600+diffOne*60+diffOTwo;
So here is the question. How to get the job done while there is a date within the time stamp?

I would construct LocalDateTime instances from it.
Then i would get the milliseconds from it and substract startTime from EndTime.
What is remaining are the milliseconds passed between the two. A DateTimeFormatter is helpful as well for this purpose.
String strMin = "2017-04-15 13:27:31";
DateTimeFormatter formatterTime = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
LocalDateTime dateTimeMin = LocalDateTime.parse(strMin, formatter);
String strMax = "2017-04-15 13:40:01";
LocalDateTime dateTimeMax = LocalDateTime.parse(strMax, formatter);
long minutes = ChronoUnit.MINUTES.between(dateMin, dateMaxto);
long hours = ChronoUnit.HOURS.between(dateMin, dateMax);
If you want to get the milliseconds:
long millisPassed = dateMax.toEpochMilli() - dateMax.toEpochMilli();

Use the java date time libraries (even the old Date class would be fine for this) to parse the string into a proper object.
Depending on the date time library you chose you can then look at the difference between them. The simplest would be something like:
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
Date date1 = sdf.parse(str1);
Date date2 = sdf.parse(str2);
long differenceInSeconds = (date2.getTime()-date1.getTime())/1000;
The new Java 8 time classes would also allow you to do this and would be better to learn going forwards. I can't remember the syntax for that off the top of my head though.

Did you try with replace all the other part of your String like this :
String[] partsMin = min.replaceAll("\\d+-\\d+-\\d+", "").trim().split(":");
String[] partMax = max.replaceAll("\\d+-\\d+-\\d+", "").trim().split(":");

Doing this in your code:
int diffZero=Integer.parseInt(partMax[0])
is the same as doing:
int diffZero=Integer.parseInt("2017-04-15")
that is generating an Exception(NumberFormatException)
you should better try to PARSE those strings min and max into a date
Edit:
you can inspect your code/ variables: and see that splitting to ":" is not giving you back the correct array since the element at index 0 is holding more information than you need...
but as I said before, you are going on the wrong path, dont re invent the wheel and look how practical will get using the APIs that java has for us:
String min = "2017-04-15 13:27:31";
String max = "2017-04-15 13:40:01";
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
LocalDateTime dateTimeMin = LocalDateTime.parse(min, formatter);
LocalDateTime dateTimeMax = LocalDateTime.parse(max, formatter);
long days = ChronoUnit.DAYS.between(dateTimeMin, dateTimeMax);
long minutes = ChronoUnit.MINUTES.between(dateTimeMin, dateTimeMax);
System.out.println(days);
System.out.println(minutes);

use SimpleDateFormat to parse the date string, and do operation on Date result, you will get right value. This works well for date between '2017-02-28 23:59:59' and '2017-03-01 00:00:01'
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
Date date1 = format.parse("2017-02-28 23:59:59");
Date date2 = format.parse("2017-03-01 00:00:01");
long time1 = date1.getTime();
long time2 = date2.getTime();
long diff = time2 - time2; // should be 2000

How to remove millisec from date and time [duplicate]

This question already has answers here:
Change date format in a Java string
(22 answers)
Closed 8 years ago.
I have a object that giving date and time in this format "2014-06-11 16:32:36.828".
I want to remove millisec .828.
In my db that object is in time stamp format but whenever i am showing i am converting it to tostring().
so how to remove millisec please help me

The following code convert "2014-06-11 16:32:36.828" into "2014-06-11 16:32:36"
new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS").parse("2014-06-11 16:32:36.828"));
Explanation:
new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS").parse("2014-06-11 16:32:36.828") parse the input string into
Wed Jun 11 16:32:36 IST 2014
new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date()) format the input date into specified structure.

I would use DateUtils.truncate(date, Calendar.SECOND)

Date d = SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS").format(yourString);
Calendar c = Calendar.getInstance();
c.setTime(d);
c.set(Calendar.MILLISECOND, 0);
return c.getTime();
I remember there is a way to directly read Date off your timestamp field but I don't do that in my everyday coding. So I'd left for others to post so. Nevertheless, you can use the same above code to translate your date from that timestamp into a date without MILLISECOND.

If you receive it as a Timestamp, you should use the appropriate formatter when converting it to a string:
String s = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(timestamp);
Note: this will use the default time zone of the local computer.

Extract epoch millis from the original Date object and do integer division by 1000 followed by multiplication by 1000. Create Date object with the time zone of the original object and the millis calculated the above suggested way.

You can get the system time as follows without milliseconds
import java.text.SimpleDateFormat;
import java.util.Calendar;
And the code
Calendar currentDate = Calendar.getInstance();
SimpleDateFormat formatter= new SimpleDateFormat("dd-MM-YYYY-hh:mm:ss");
String dateNow = formatter.format(currentDate.getTime());
System.out.println(dateNow);

if you want to mantain the format try something like that:
public static String getFechaTimestampToString (Timestamp timestamp) {
String date = "";
Calendar cal = Calendar.getInstance();
cal.setTime(new Date(timestamp.getTime()));
int year = cal.get(Calendar.YEAR);
int month = cal.get(Calendar.MONTH)+1;
int day = cal.get(Calendar.DAY_OF_MONTH);
String monthstr = "";
String daystr = "";
if(month<10)
monthstr = "0"+month;
else
monthstr = ""+month;
if(day<10)
daystr = "0"+day;
else
daystr = ""+day;
date = year + "-" + monthstr + "-" + daystr ;
return date;
}
To reverse data to database:
public static Timestamp getFechaStringToTimestamp (String strDate) {
Timestamp timestamp = null;
strDate = strDate + " 00:00:00";
timestamp = Timestamp.valueOf(strDate);
return timestamp;
}

Java convert date to EST timezone to respecting DST

I want to get the current date converted to America/Montreal timezone. I'm doing it like this:
Date date = new Date();
TimeZone timeZone = TimeZone.getTimeZone ("America/Montreal");
Calendar cal = new GregorianCalendar(timeZone);
cal.setTime(date);
String whatIWant = "" + cal.get(Calendar.HOUR_OF_DAY) + ':'+
cal.get(Calendar.MINUTE)+ ':'+ cal.get(Calendar.SECOND);
log.info(whatIWant);
The conversion is just fine but I was wondering how robust this code is. What will happen when in no daylight saving?

That code is fine. Java automatically takes winter time or summer time into account.
You could also do this by using a DateFormat object to convert the date to a string, setting the desired time zone on the DateFormat object:
Date date = new Date();
DateFormat df = new SimpleDateFormat("HH:mm:ss");
// Tell the DateFormat that you want the time in this timezone
df.setTimeZone(TimeZone.getTimeZone("America/Montreal"));
String whatIWant = df.format(date);