How to Convert DurationFormatUtils back to Milliseconds

Currently I have been using DurationFormatUtils to convert the Millis in a track into HH:mm:ss, but I want to allow the user to seek the track using this format, for example they would type: ‘-seek HH:mm:ss or mm:ss’ and I want to convert that time back into milliseconds… Are there any built in Java methods to do this? Or would I have to create my own method to convert it?

Answer

You can do it like this.

First, define a DateTimeFormatter instance.

DateTimeFormatter dtf =
        DateTimeFormatter.ofPattern("H:mm:ss");

• H – one or two digits of 24 hour time
• mm – minutes
• ss – seconds

To handle absence of the hours you can check to see if a colon exists from the 3rd character on. If it does, then the time can be parsed as is, otherwise, prepend 00 hours. I chose to put it in a lambda.

Function<String,String> adjust = time -> time.indexOf(":",3) >= 0 
            ? time : "00:"+time;

Putting it all together.

String[] times = { "3:49:44", "12:30" };
for (String time : times) {
    int millis = dtf.parse(adjust.apply(time))
          .get(ChronoField.MILLI_OF_DAY);
    System.out.println(millis);
}

prints

13784000
750000

Check out the java.time package for more date/time classes.