How to convert time stamp to get exact milliseconds difference in Android?

Question

I have time in this format: If I have times like Y1 = 05:41:54.771 and Y2 = 05:42:03.465, I want to have exact difference in milliseconds. For the above example the exact millisecond difference would be "6693 milliseconds". How do I achieve this?

            Date date = new Date(timestamp);
  DateFormat format = new SimpleDateFormat("hh:mm:ss.SSS",Locale.getDefault());
       
    
} 
    

Answer 1

The date-time API of java.util and their formatting API, SimpleDateFormat are outdated and error-prone. It is recommended to stop using them completely and switch to the modern date-time API.

• For any reason, if you have to stick to Java 6 or Java 7, you can use ThreeTen-Backport which backports most of the java.time functionality to Java 6 & 7.
• If you are working for an Android project and your Android API level is still not compliant with Java-8, check Java 8+ APIs available through desugaring and How to use ThreeTenABP in Android Project.

Using the modern date-time API:

import java.time.Duration;
import java.time.LocalTime;

public class Main {
    public static void main(String[] args) {
        long millisBetween = Duration.between(LocalTime.parse("05:41:54.771"), LocalTime.parse("05:42:03.465"))
                                .toMillis();
        System.out.println(millisBetween);
    }
}

Output:

8694

Learn more about the modern date-time API from Trail: Date Time.

Using the legacy API:

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Locale;

public class Main {
    public static void main(String[] args) throws ParseException {
        DateFormat sdf = new SimpleDateFormat("HH:mm:ss.SSS", Locale.ENGLISH);
        long millisBetween = sdf.parse("05:42:03.465").getTime() - sdf.parse("05:41:54.771").getTime();
        System.out.println(millisBetween);
    }
}

Output:

8694

Some important notes about this solution:

1. Without a date, SimpleDateFormat parses the time string with a date of January 1, 1970 GMT.
2. Date#getTime returns the number of milliseconds since January 1, 1970, 00:00:00 GMT represented by this Date object.
3. Use H instead of h for a time value in 24-Hour format.

Answer 2

You are in the right direction. Using the DateFormat's parse() method you can get a Date object. Then convert it to instant and get the millis since epoch. Finally it's a simple subtraction.

DateFormat format = new SimpleDateFormat("hh:mm:ss.SSS", Locale.getDefault());

try {
    Instant y1 = format.parse("05:41:54.771").toInstant();
    Instant y2 = format.parse("05:42:03.465").toInstant();

    long diffMillis = y2.toEpochMilli() - y1.toEpochMilli();
    System.out.println(diffMillis);

} catch (ParseException e) {
    throw new RuntimeException(e);
}

Answer 3

The line of code you have provided is a DateFormat object that takes a date and formats it into a string representation. It doesn't have any actual data stored in it. You want to make a comparison on the actual date object, not the formatter.

There are a few different ways to store time, but a common way to store timestamps is as a Long. Since longs are numbers, you can do comparison and math just like an Int:

Long startTime = System.currentTimeMillis();
// Do some long task here that we want to know the duration of
Long endTime = System.currentTimeMillis();

Long difference = endTime - startTime;

Alternatively, there are libraries and tools for dealing with structured time data that may have other ways of storing timestamps and comparing them, however this is a quick example of a common simple implementation if you just need to quickly compare two timestamps.