在特定的十进制数中舍入小数java

Question

How to get correct time when subtracting decimal numbers. I wanted to subtract numbers as if it were tiime. But time only goes to 60 minutes whereas numbers to 100. How could I put some sort of restriction on the decimal places to make it like time.

Answer 1

Here's one way. The elapsed time is in milliseconds, as that is what you have when you subtract a start System.currentTimeMillis() from a finish System.currentTimeMillis().

public String formatElapsedTime(long elapsedTime) {
    int centiseconds = (int) (((elapsedTime % 1000L) + 5L) / 10L);
    centiseconds %= 10;
    int seconds = (int) (elapsedTime / 1000L);
    int minutes = seconds / 60;
    seconds -= minutes * 60;
    int hours = minutes / 60;
    minutes -= hours * 60;

    if (hours > 0) {
        return String.format("%2d:%02d:%02d.%02d", hours, minutes, seconds,
                centiseconds);
    } else if (minutes > 0) {
        return String.format("%2d:%02d.%02d", minutes, seconds,
                centiseconds);
    } else {
        return String.format("%2d.%02d", seconds, centiseconds);
    }
}

You probably don't need to display centiseconds when you're measuring elapsed time in hours.

Because my format strings start with “%2d”, seconds, minutes, and hours less than 10 have a space as the first character of the string. I find this keeps the display from jumping so much. If you don't want the leading space, change the format String to “%1d”.

You can calculate days as well, for really long elapsed times. You would probably want a format like “3 days, 6 hours, 25 minutes, and 13 seconds”. Or not.