经过时间格式HH：mm：ss

Question

It's a simple problem but I'm not getting it to work.

I'm incrementing a variable each second and setting it in a GregorianCalendar in miliseconds.

And I'm using this format HH:mmss to present the elpased time.

The problem is that the hour starts showing 01 instead of 00. For instance, after 1 minute and 35 seconds what is shown is: 01:01:35 instead of 00:01:35 .

Where could be the problem?

There is the important code:

GregorianCalendar timeIntervalDone = new GregorianCalendar(TimeZone.getTimeZone("GMT-1")); //initially I didn't have the TimeZone set, but no difference
SimpleDateFormat dateTimeIntervalFormat = new SimpleDateFormat("HH:mm:ss");

public String getTimeIntervalDoneAsString() {
    timeIntervalDone.setTimeInMillis(mTimeIntervalDone); //mTimeIntervalDone is the counter: 3seccond -> mTimeIntervalDone = 3000
    return dateTimeIntervalFormat.format(timeIntervalDone.getTime());
}

Answer 1

I think the reason is you set the time zone to GMT-1, but the output is utc. Please try it without that time zone and it should work.

Answer 2

I finally got it:

GregorianCalendar timeIntervalDone = new GregorianCalendar(); 
SimpleDateFormat dateTimeIntervalFormat = new SimpleDateFormat("HH:mm:ss");
dateTimeIntervalFormat.setTimeZone(TimeZone.getTimeZone("GMT"));

Answer 3

Your approach is a hack, trying to use a date-time moment class ( GregorianCalendar ) to represent a span of time. Plus your format is ambiguous, looking like a time-of-day rather than a duration.

ISO 8601

An alternative is to use the ISO 8601 standard way of describing a duration: PnYnMnDTnHnMnS where the P marks the beginning and the T separates the year-month-day portion from hour-minute-second portion.

java.time

The java.time framework in Java 8 and later supplants the old java.util.Date/.Calendar classes. The old classes have proven to be troublesome, confusing, and flawed. Avoid them.

The java.time framework is inspired by the highly-successful Joda-Time library, defined by JSR 310 , extended by the ThreeTen-Extra project, and explained in the Tutorial .

The java.time framework does use ISO 8601 as its defaults, this otherwise excellent set of classes lacks a class to represent an entire period of years-months-days-hours-minutes-seconds. Instead it breaks the concept into two. The Period class handles years-months-days while the Duration class handles hours-minutes-seconds.

Instant now = Instant.now ();
Instant later = now.plusSeconds ( 60 + 35 ); // One minute and 35 seconds later.

Duration duration = Duration.between ( now , later );
String output = duration.toString ();

Dump to console.

System.out.println ( "output: " + output );

output: PT1M35S