convert milliseconds to seconds, minutes without rounding

Question

I'm trying to convert milliseconds to seconds and minutes in Java 1.4.2. I'm having trouble because my conversions are being rounded up. For example....

public String toString() {

    long startTime = System.currentTimeMillis();
    long endTime = System.currentTimeMillis();
    long elapsedTimeMillis = (endTime - startTime);

    double seconds = (double) (elapsedTimeMillis / 1000) % 60 ;
    double minutes = (double) ((elapsedTimeMillis / (1000*60)) % 60);

    return 
        " elapsedTime: " 
        + " milliseconds:" + elapsedTimeMillis 
        + " seconds:" + seconds 
        + " minutes:" + minutes;

}

This returns results like...

elapsedTime: milliseconds:1392 seconds:1.0 minutes:0.0

and

elapsedTime: milliseconds:742 seconds:0.0 minutes:0.0123667

Instead I would like...

elapsedTime: milliseconds:1392 seconds:1.392 minutes:0.0232

and

elapsedTime: milliseconds:742 seconds:0.742 minutes:0.01236667

Seems like a simple question but I'm not sure what I'm doing wrong. Can someone help me with this.

thanks

It does no good to convert to double *after* you've done the division. — Hot Licks, Sep 12 '14 at 02:05
(But your computations are wrong anyway. Better to compute integer seconds and compute fractions separately.) — Hot Licks, Sep 12 '14 at 02:06
Check 1st answer of this link, https://stackoverflow.com/questions/10874048/from-milliseconds-to-hour-minutes-seconds-and-milliseconds . — Nazmus Saadat, Jun 12 '18 at 06:34

score 2 · Accepted Answer · edited Sep 12 '14 at 02:14

2

Use floating point arithmetics on division:

(elapsedTimeMillis/1000.0)

and

(elapsedTimeMillis/(1000.0*60))

correspondingly.

In other words:

double seconds =  elapsedTimeMillis / 1000.0;
double minutes = (elapsedTimeMillis / (1000.0 * 60)) % 60;

edited Sep 12 '14 at 02:14

Yohanes Khosiawan 许先汉

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answered Sep 12 '14 at 02:03

user3159253

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2

The seconds calculation is just plain wrong, and using 1000.0 doesn't solve the underlying problem, which is that floating-point shouldn't be used at all. – user207421 Sep 12 '14 at 02:54
why is the seconds calcuation plain wrong? Can you please expand on this comment – Richie Sep 15 '14 at 00:18

convert milliseconds to seconds, minutes without rounding

1 Answers1