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How to calculate relative time spans using Java (code converting problem)? [duplicate]

This question already has answers here:
Java 8: Difference between two LocalDateTime in multiple units
(11 answers)
Closed 2 years ago.
I decided to give myself a challenge on Java that implements this question's achievement.
The things I have to do is get LocalDateTime, convert the same code from the linked question's answers, then receiving a string from the function.
Here's what I've done so far:
public static String relTime(LocalDateTime now)
{
// accepted answer converted to Java
const int min = 60 * SECOND;
const int hour = 60 * MINUTE;
const int day = 24 * HOUR;
const int mon = 30 * DAY;
// still don't know how to convert this method
var ts = new TimeSpan(DateTime.UtcNow.Ticks - yourDate.Ticks);
double delta = Math.Abs(ts.TotalSeconds);
if (delta < 1 * MINUTE)
return ts.Seconds == 1 ? "one second ago" : ts.Seconds + " seconds ago";
if (delta < 2 * MINUTE)
return "a minute ago";
if (delta < 45 * MINUTE)
return ts.Minutes + " minutes ago";
if (delta < 90 * MINUTE)
return "an hour ago";
if (delta < 24 * HOUR)
return ts.Hours + " hours ago";
if (delta < 48 * HOUR)
return "yesterday";
if (delta < 30 * DAY)
return ts.Days + " days ago";
if (delta < 12 * MONTH)
{
int months = Convert.ToInt32(Math.Floor((double)ts.Days / 30));
return months <= 1 ? "one month ago" : months + " months ago";
}
else
{
int years = Convert.ToInt32(Math.Floor((double)ts.Days / 365));
return years <= 1 ? "one year ago" : years + " years ago";
}
}
The only problem that I should encounter is from var ts = new TimeSpan(DateTime.UtcNow.Ticks - yourDate.Ticks);.
Although I read 2 questions from Stack Overflow finding equivalents of TimeSpan and Ticks, I baely have any ideas how to properly convert the line of code. Also, I have to get a double which will need math.abs() to get TotalSeconds which I can't really find a proper way to deal with either, but I did find ZoneOffset.ofTotalSeconds and still don't know how to deal with it.
So how can I convert this properly?
var ts = new TimeSpan(DateTime.UtcNow.Ticks - yourDate.Ticks);
double delta = Math.Abs(ts.TotalSeconds);

You need to gain a deeper understanding of what this method actually does. Literally translating code from C# to Java won't give you a good solution and gets you stuck on language-specific details.
The two lines basically calculate the (absolute) difference in seconds of a timestamp to the current time. This can be written in Java as follows:
Duration duration = Duration.between(LocalDateTime.now(), timestamp);
long delta = duration.abs().getSeconds();
I'm just addressing your actual question here on how to transform these two lines. The provided snippet is not valid Java code and some parts are missing. delta is the difference in seconds which does not necessarily need to be a double. The argument you pass to your method should be named anything else than now because this is the timestamp you want to compare to the current time inside the method.

You could use SimpleDateFormat to create a nice display format (use something like "HH hours, mm minutes and ss seconds ago" for the format (not sure if this exact example works)). You could also use Instant to get the current time, and you can use Instant.now().minusSeconds(Instant.now().minusSeconds(seconds).getEpochSeconds()) for the time difference (or just use System.currentTimeMillis() and multiply by 1000).
Alternatively, you could use Duration and write a custom display format using getSeconds() and getHours() etc.

Dividing seconds by 60 twice to get hours results in zero

I'm trying to convert the number of seconds contained in a duration into hours by dividing the duration.getSeconds() value by 60 twice.
However when I do this the number is being converted into 0.0, instead of an actual value. I imagine this is because the number is too small to be represented, however I have used doubles to try and represent the number and it still doesn't work.
In the below code please assume startTime and endTime are valid LocalTimes produced by two separate calls to LocalTime.now()
Duration duration = Duration.between(startTime, endTime); //duration in sec
double durationInSec = duration.getSeconds();
double durationInHours = durationInSec / 60 / 60;

Works for me
LocalTime start = LocalTime.of ( 11 , 30 );
LocalTime stop = start.plusHours ( 2 );
Duration d = Duration.between ( start , stop );
double seconds = d.toSeconds ();
double hours = seconds / 60 / 60;
See this code run live at IdeOne.com.
start.toString() = 11:30
stop.toString() = 13:30
d.toString() = PT2H
seconds = 7200.0
hours = 2.0
Tip: When you know you want to work with fractions of double, append d to your numeric literals to avoid any confusion over the compiler's integer-to-fraction conversion and up/downscaling the types. Be explicit. So in your code, append each 60 with a d. May not be necessary here, but removes ambiguity for the reader at least.
double hours = seconds / 60d / 60d ;
<1 second = 0 hours
As others commented, if your elapsed time was less than a full second, your code results in a zero.
A Duration is internally represented by a count of whole seconds plus a fractional second as a count of nanoseconds. Your call to Duration::getSeconds() retrieves the whole seconds, without the fractional second. So for a duration of PT0.5S, getSeconds returns zero. Zero divided by sixty divided by sixty equals zero.
Duration d = Duration.parse ( "PT0.5S" ); // Half a second.
double hours = d.getSeconds () / 60d / 60d;
hours: 0.0
You should instead call Duration::toNanos to get a total number of nanoseconds elapsed. And adjust your division.
Duration d = Duration.parse ( "PT0.5S" ); // Half a second.
long nanos = d.toNanos () ;
double hours = nanos / 1_000_000_000d / 60d / 60d ;
hours: 1.388888888888889E-4
Avoid fractional hours
By the way, let me suggest that fractional hours is a poor way to handle spans-of-time. Hours, minutes, seconds, and such are not amenable to such decimal math.
Besides that, the floating-point types such as double are inherently inaccurate.
Use the Java classes intended for this purpose: Duration and Period. When reporting or exchanging textually the value of these objects, use standard ISO 8601 format. As seen above, 2 hours is represented by PT2H.
The java.time classes use ISO 8601 formats by default when parsing/generating strings. No need to specify a formatting pattern.
Duration d = Duration.parse( "PT2H" ) ;

How to countdown to a date in java? [duplicate]

This question already has answers here:
Timer - counting down and displaying result in specific format [duplicate]
(2 answers)
Closed 6 years ago.
So i am creating an application to countdown to a date in java.
So lets say i parse these 2 days:
Date Now = 2016/01/15 16:52:22
Date End = 2016/01/15 18:37:18
How would i calculate the differences so that i can get the output like so:
1 hour, 44 minutes and 56 seconds
instead of the total hours, total minutes and total seconds.
I guess the best way to explain it is that i need to get the seconds left of the minute, the minutes left of the hour, etc, etc.

You haven't specify your date format. Supposed you use the Date class, the following code gives you a difference in milliseconds.
long difference = dateEnd.getTime() - dateNow.getTime();
Then you approach to your result with a simple calculation:
int seconds = (int) (difference / 1000) % 60 ;
int minutes = (int) ((difference / (1000*60)) % 60);
int hours = (int) ((difference / (1000*60*60)) % 24);

Convert Minutes to Hours using JodaTime

I'm having Minutes in java.lang.Long and want to convert this value to java.math.BigDecimal, ie. as Hours.
BigDecimal hours = BigDecimal.valueOf(minutes)
.divide(BigDecimal.valueOf(DateTimeConstants.MINUTES_PER_HOUR))
.setScale(2,RoundingMode.HALF_DOWN);
Tried the above method. It return hours, but no the way actually i want it
How i need is :
240 Minutes : 4 Hours
230 Minutes : 3.50 hours
Any help?

I would convert your Minutes to a Period object:
Minutes minutes = ...;
Long millisec = minutes*60*1000;
Period period = new Period(millisec);
Then use the Period object you can ask the Hours. Anything you want...

Note: 230 minutes is not 3.50 hours, it's 3.83 hours, i'm assuming you mean "3 hours and 50 minutes".
So what you want is the hh:mm representation.
You don't need BigDecimals. Use this:
long minutes = 230;
long hours = minutes / 60;
long minnutesRemaining = minutes % 60;
System.out.println(hours + "." + minnutesRemaining);

I'm betting the OP actually wants to convert minutes into hours and minutes. This is as easy as:
int minutes = 230;
System.out.println(
String.format("%d Minutes: %d:%02d Hours", minutes, (minutes/60), (minutes%60)));
Just printing the minutes divided by 60 (using integer arithmetic) and the modulo of minutes divided by 60 (formatted as two digits with leading zeros by the "%02d" format.

You can do this using BigDecimal easy. You can use divideAndRemainder()
long minutes = 230L;
BigDecimal min = new BigDecimal(minutes);
BigDecimal constant = new BigDecimal(60);
BigDecimal[] val=min.divideAndRemainder(constant);
System.out.println(val[0]+"."+val[1]+" Hours");
Out put:
3.50 Hours

I don't know in what universe 230 minutes equals 3.5 hours, so I'm afraid that some string manipulation is your best bet:
BigDecimal hours = new BigDecimal(
String.format("%d.%d", minutes / 60, minutes % 60));
Printing out the value of hours yields 3.50, as per your requirement.

Use integer and modulo arithmetic:
long hours = minutes / 60; /*implicit round-down*/
long numberAfterDecimal = (minutes % 1.0 /*pull out the remainder*/) * 60;
Then format these two numbers as you wish.

Represent date from long, starting from year 0 instead of 1970 [duplicate]

This question already has an answer here:
How to calculate difference between two dates in years...etc with Joda-Time
(1 answer)
Closed 8 years ago.
I have a long-variable which represents an amount of delay in milliseconds. I want to transform this long to some kind of Date where it says how many hours, minutes, seconds, days, months, years have passed.
When using Date toString() from Java, as in new Date(5).toString, it says 5 milliseconds have passed from 1970. I need it to say 5 milliseconds have passed, and 0 minutes, hours, ..., years.

you cannot get direct values , without any reference date for your requirements, you need define first reference value like below:
String dateStart = "01/14/2012 09:29:58";
SimpleDateFormat format = new SimpleDateFormat("MM/dd/yyyy HH:mm:ss")
Date d1 = format.parse(dateStart);
the above is your reference date , now you need to find the current date and time using following.
long currentDateTime = System.currentTimeMillis();
Date currentDate = new Date(currentDateTime);
Date d2.format(currentDate)
and the difference of these values like long diff=d2-d1 will gives values in milliseconds.
then
long diffSeconds = diff / 1000 % 60;
long diffMinutes = diff / (60 * 1000) % 60;
long diffHours = diff / (60 * 60 * 1000) % 24;
long diffDays = diff / (24 * 60 * 60 * 1000);
and similarly for months and years.
you can also refer the example given on this link for more information http://javarevisited.blogspot.in/2012/12/how-to-convert-millisecond-to-date-in-java-example.html

From what I understand from your question you could achieve your goal by writing a method that will suit your needs i.e.:
static public String dateFromMili (long miliseconds) {
// constants that will hold the number of miliseconds
// in a given time unit (year, month etc.)
final int YEAR_IN_MILISECONDS = 12*30*24*60*60*1000;
final int MONTH_IN_MILISECONDS = 30*24*60*60*1000;
final int DAY_IN_MILISECONDS = 24*60*60*1000;
final int HOUR_IN_MILISECONDS = 60*60*1000;
final int MINUTE_IN_MILISECONDS = 60*1000;
final int SECONDS_IN_MILISECONDS = 1000;
// now use those constants to return an appropriate string.
return miliseconds +" miliseconds, "
+miliseconds/SECONDS_IN_MILISECONDS+" seconds, "
+miliseconds/MINUTE_IN_MILISECONDS+" minutes, "
+miliseconds/HOUR_IN_MILISECONDS+" hours, "
+miliseconds/DAY_IN_MILISECONDS+" days, "
+miliseconds/MONTH_IN_MILISECONDS+" months, "
+miliseconds/YEAR_IN_MILISECONDS+" years have passed";
}
Than you will have to pas the number of miliseconds as a parameter to your new function that will return the desired String (i.e for two seconds):
dateFromMili (2000);
You could also print your answer:
System.out.println(dateFromMili(2000));
The result would look like this:
2000 miliseconds, 2 seconds, 0 minutes, 0 hours, 0 days, 0 months, 0 years have passed
Note that this method will return Strings with integer value (you will not get for example "2.222333 years" but "2 years"). Furthermore, it could be perfected by changing the noun from plural to singular, when the context is appropriate ("months" to "month").
I hope my answer helped.

This is how I solved the problem:
I used a library called Joda-Time (http://www.joda.org/joda-time/) (credits to Keppil!)
Joda-Time has various data-structures for Date and Time. You can represent a date and time by a DateTime-object.
To represent the delay I was looking for, I had two options: a Period data-structure or a Duration data-structure. A good explanation of the difference between those two can be found here: Joda-Time: what's the difference between Period, Interval and Duration? .
I thus used a Duration-object, based on the current date of my DateTime-object. It has all the methods to convert the amount of milliseconds to years, months, weeks, days, hours, minutes and seconds.