Java: Why isn't String.format() working on this Long variable?

Question

I am simply trying to get milliseconds to display the first two digits of the variable.

What I expect to work (I see two digits initially, then as it is incremented I see three digits):

@Override
public String toString() {
    Long milliSeconds = TimeUnit.MILLISECONDS.toMillis(elapsedTime) % 1000;
    Long seconds = (TimeUnit.MILLISECONDS.toSeconds(elapsedTime));
    return String.format("%2d.%02d seconds", seconds, milliSeconds);
}

What actually works:

@Override
public String toString() {
    String milliSeconds = String.format("%02d",
            TimeUnit.MILLISECONDS.toMillis(elapsedTime) % 1000).substring(0, 2);
    Long seconds = (TimeUnit.MILLISECONDS.toSeconds(elapsedTime));
    return String.format("%2d.%s seconds", seconds, milliSeconds);
}

Or:

@Override
public String toString() {
    double milliSeconds = (double)(TimeUnit.MILLISECONDS.toMillis(elapsedTime) % 1000) / 1000;
    Long seconds = (TimeUnit.MILLISECONDS.toSeconds(elapsedTime));
    return String.format("%.2f seconds", seconds + milliSeconds);
}

I guess my first question would be are either of my solutions that work more resource intensive than the one that doesn't? And secondly, what am I doing wrong in the first solution? I would expect %02d to take the long and truncate it to 2 digits buffered with a 0. Instead I see the two digits plus a trailing 0.

mrres1 · Accepted Answer · 2014-04-29 03:00:20Z

2

System.out.printf("%07.3f seconds", (elapsedTime / 1000f));

answered Apr 29, 2014 at 3:00

mrres1

1,1556 silver badges10 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Jens Bodal Over a year ago

Thanks, elapsedTime was a Long but this works: return String.format("%.2f seconds", (float)elapsedTime / 1000f);

mrres1 Over a year ago

If one of the operands is a floating point and the other is an integer then the result will be a floating point. The literal on the 1000 will define it as a float, there is also d and l for double and long.

Hovercraft Full Of Eels · Accepted Answer · 2014-04-29 02:20:05Z

2

milliseconds should be %03d not %02d.

If you want the resolution to be at the tens of milliseconds level, then you'll have to do a little "fancy" calculating.

return String.format("%2d.%02d seconds", seconds, milliSeconds / 10);

answered Apr 29, 2014 at 2:20

Hovercraft Full Of Eels

286k25 gold badges268 silver badges391 bronze badges

Collectives™ on Stack Overflow

Java: Why isn't String.format() working on this Long variable?

2 Answers 2

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related