Converting Timestamps to Formatted Time in Java

You encounter a common task in programming: converting a timestamp, usually represented as milliseconds since a specific point in time (often the epoch), into a human-readable string. In this case, you specifically want to convert into a format displaying hours, minutes, seconds, and milliseconds (h:m:s:ms).

To achieve this conversion, the first step is to convert the long timestamp into a Date object. This can be done using the constructor Date(long timestamp).

Date date = new Date(logEvent.timestamp);

Next, create a SimpleDateFormat object to specify the desired output format. This format specifies how the date should be formatted, with hours, minutes, seconds, and milliseconds.

DateFormat formatter = new SimpleDateFormat("HH:mm:ss.SSS");

Optionally, you can specify a timezone for the formatter to ensure the time is displayed in the correct timezone.

formatter.setTimeZone(TimeZone.getTimeZone("UTC"));

Finally, you can format the date using the format method of the SimpleDateFormat object.

String dateFormatted = formatter.format(date);

This code will produce a string in the h:m:s:ms format, such as "00:20:00.000" for a timestamp of 1200 milliseconds.