Develop Reference

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.

Loss of precision - Java

Problem Statement:
Write a method whatTime, which takes an int, seconds, representing the number of seconds since midnight on some day, and returns a String formatted as "::". Here, represents the number of complete hours since midnight, represents the number of complete minutes since the last complete hour ended, and represents the number of seconds since the last complete minute ended. Each of , , and should be an integer, with no extra leading 0's. Thus, if seconds is 0, you should return "0:0:0", while if seconds is 3661, you should return "1:1:1"
My Algorithm:
Here is how my algorithm is supposed to work for the input 3661:
3661/3600 = 1.016944 -> This means the number of hours is 1
Subtract the total number of hours elapsed i.e. 1.016944-1=0.016944
Multiply this with 60 i.e. 0.016944*60=1.016666 -> The number of minutes elapsed is equal to 1
Subtract the total number of minutes elapsed i.e. 1.01666-1=0.01666. Multiply this with 60. This would yield the number of seconds elapsed.
The output produced however is 1:1:0. I tried to use a print statement and it appears that the value of 'answer3' variable is 0.999 and that is why prints the integer part (0). I tried to use the Math.ceil() function to round up the value and it produces a correct output. However I can only score about 60/250 points when I submit my code (TopCoder SRM 144 Div2) . Any insight for improving the algorithm will be helpful.
public class Time
{
public String whatTime(int seconds)
{
double answer1,answer2,answer3; int H;
answer1=(double)seconds/3600;
H=(int)answer1;
answer2=(double)((answer1-H)*60);
int M=(int)answer2;
answer3=answer2-M;
answer3=(double)answer3*60;
int S=(int)answer3;
String answer=Integer.toString(H);
answer=Integer.toString(H)+":"+Integer.toString(M)+":"+Integer.toString(S);
return answer;
}
}

public String whatTime(int seconds) {
int secondVal = seconds % 60;
int minutes = seconds / 60;
int minuteVal = minutes % 60;
int hours = minutes / 60;
int hourVal = hours % 24;
int daysVal = hours / 24;
String answer = "" + daysVal + ":" + hourVal + ":" + minuteVal + ":" + secondVal;
return answer;
}
Could do the formatting more elegantly, but that's the basic idea.

Avoid floating point values, and work entirely with ints or longs.

You could solve this by working with ints :
3661/3600 = 1.016944 -> This means the number of hours is 1
Subtract the number of hours * 3600 - i.e. 3661-(1*3600) = 61
61/60 = 1.0166666 -> The number of minutes elapsed is equal to 1
Subtract the number of minutes * 60 i.e. 61-(1*60)=1. This yields the number of seconds elapsed.

Using a Ternary Operator to a "0" within the statement

I'm trying to format a time using a variable input. If a user enter an hour as 1 - 9 the out put would include a "0", and the same for minutes. So far if a user enters 1 hour 3 minutes the output reads 1:3 instead of 01:03.
How do I get the extra 0 in front of numbers less than 10.
Here's the code.....
import java.util.Scanner;
public class FormatTime {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int MinutesInput;
int HoursInput;
int Hours;
int Minutes;
{
System.out.println("Enter hours between 1 and 24");
Hours = input.nextInt();
System.out.println("Enter minutes between 1 and 59");
Minutes = input.nextInt();
{
**//THIS NEXT LINE IS THE PROBLEM**
HoursInput = Hours < 10 ? "0" + Hours : Hours;
System.out.print(HoursInput + ":");
}
{
**//THIS NEXT LINE IS THE PROBLEM**
MinutesInput = (Minutes < 10) ? "0" + Minutes : (Minutes);
System.out.print(MinutesInput);
}
System.out.println();
}
}
}

How do I get the extra 0 in front of numbers less than 10.
You don't, while the target variable is of type int. An int is just a number, not a string - whereas "0" + Hours is a string.
int values don't contain any sort of string representation - the number sixteen is just as much "0x10" or "0b10000" as it is "16"... or even "00016" if your decimal representation allows much digits. ("00016" may be mis-interpreted as fourteen, however, if it's parsed as an octal string...)
Use DecimalFormat to convert numbers into strings in your desired format, or String.format, or possibly just PrintStream.printf if you want to write it straight to the console.
I'd also strongly recommend that you use camelCase for your local variables, and only declare them when you first need them.

Perhaps you should be using
System.out.printf("%02d:%02d%n", Hours, Minutes);

You are confusing int and String types:
int HoursInput;
//...
HoursInput = Hours < 10 ? "0" + Hours : Hours;
There are two problems with your code: you are trying to store string "07" (or similar) in an int. Secondly even if it was possible, 07 is equivalent to 7 as far as integer types are concerned (well, leading 0 has a special octal meaning, but that's not the point).
Try this instead:
String hoursInput;
//...
hoursInput = Hours < 10 ? "0" + Hours : "" + Hours;

you must use String variables or use format method (similar to sprintf from c) from String class.
String time = String.format("%02d:%02d", hours, minutes );

How to use a Time format in Android

I am trying to take have a time that counts down all the way to 0 from 1 minute.
I have already created my timer. I just need to know how do i convert a int such as 100 to a String to show 1:00 as in a minute and keep counting down like minus 1 secodn from the int and convert it to the String :59?
Any suggestions?

If I understand your question correctly you simply want to divide your number by 60 to get the minutes and then mod your number by 60 to get the seconds and then concat the strings.
int remainingTime = 100;// or whatever number of seconds you have left
String min = (remainingTime / 60) + "";
String sec = (remainingTime % 60) + "";
String remainingTimeStamp = "min" + ":" + "sec";
If you want to get fancy with it, check to see if min and sec are less than 10 and append a leading zero, so that it looks like 01:05 rather than 1:5
I'm not sure what you mean by "I already have my timer". I'll wait for you to update your question, rather than speculate as to what you might mean, before I continue elaborating.

To add to this, check the http://developer.android.com/reference/android/text/format/DateUtils.html class. Note that this is not in 'org.apache' which has another DateUtils class.

Edit:
Since it appears you were looking for formatting 100 seconds here is it formatted:
SimpleDateFormat df = new SimpleDateFormat("mm:ss");
String formatted = df.format(remainingTime * 1000);

JodaTime Calculate total hours worked in a week

Currently I have a function which can take the start time and end time of one day, and calculate the difference between the two, giving me the hours worked in a day. What I would like to do is be able to get the hours worked for 7 days, and return a grand total, while remaining with the display format (HH:mm).
My function for a single day's total:
Period p = new Period(this.startTime[dayIndex], this.endTime[dayIndex]);
long hours = p.getHours();
long minutes = p.getMinutes();
String format = String.format("%%0%dd", 2);//Ensures that the minutes will always display as two digits.
return Long.toString(hours)+":"+String.format(format, minutes);
this.startTime[] & this.endTime[] are both arrays of DateTime objects.
Any suggestions?

You'll need something to hold a week's worth of days, and call your function once for each day.
But that means you'll want to refactor so that your calculator method doesn't format as a string, but instead returns a numeric value, so you can easily add them together.

Another simple solution:
Here is a method that receives separate the hours and minutes.The parameters are:
Start Hour
Start Minutes
End Hour
End Minutes
first, calculate the difference between hours and minutes separate:
int hours = pEndHour - pStartHour;
int minutes = ((60 - pStartMinutes) + pEndMinutes) - 60;
then, validates if the value of "minutes" variable is negative:
// If so, the "negative" value of minutes is our remnant to the next hour
if (minutes < 0) {
hours--;
minutes = 60 + minutes ;
}
Finally you can print the period of time in the hour format:
String format = String.format("%%0%dd", 2);
System.out.println( "*** " + hours + " : " + minutes);
That's all.

Solution I ended with for those interested
Period[] p=new Period[7];
long hours = 0;
long minutes =0;
for(int x=0; x<=this.daysEntered;x++)
{
p[x] = new Period(this.startTime[x], this.endTime[x]);
hours += p[x].getHours();
minutes += p[x].getMinutes();
}
hours += minutes/60;
minutes=minutes%60;
String format = String.format("%%0%dd", 2);
return Long.toString(hours)+":"+String.format(format, minutes);