Calculating download time

[K Parsons]

Hi. I new to Java and learning on my own from a book. One of the exercises is to calculate the download time of a 50MB file. I have figured out the hours and minutes but my seconds are off. Here is the code:

import java.util.Scanner;
import java.math.BigDecimal;

public class DownloadTime
{
public static void main( String parameters[] )
{
final double KB_PER_SEC = 5.2;

double hours = 0;
double minutes = 0;
double seconds = 0;
double megabytes = 0;
double kilobytes = 0;
double totalSeconds = 0;
Scanner sc = new Scanner( System.in );
String choice = "n";

do
{
System.out.print( "\n\nEnter the size of the file in megabytes(MB): " );
megabytes = sc.nextDouble();

// Convert megabytes to kilobytes because the value to divide must be in seconds. The division of
// kb and KB_PER_SEC will cancel out the kilobytes and leave only seconds, which is what we want.
kilobytes = megabytes * 1024;
totalSeconds = kilobytes / KB_PER_SEC;

// There are 3600 seconds in one hour so divide the total
// number of seconds by 3600 to get the number of hours.
hours = totalSeconds / 3600;

// The minutes are the remainder that's left after getting the hours. Since
// there are 60 seconds in one minute divide that remainder by 60.
minutes = ( totalSeconds % 3600 ) / 60;

// The seconds are what's left over after getting the hours and minutes.
seconds = ( totalSeconds % 3600 ) - ( minutes * 60 );

//// Convert megabytes to kilobytes because the value to divide must be in seconds. The division of
//// kb and KB_PER_SEC will cancel out the kilobytes and leave only seconds, which is what we want.
//kilobytes = megabytes * 1024;
//BigDecimal bdKilobytes = new BigDecimal( Double.toHexString( kilobytes ) );
//bdKilobytes = bdKilobytes.
//totalSeconds = kilobytes / KB_PER_SEC;
//
//// There are 3600 seconds in one hour so divide the total
//// number of seconds by 3600 to get the number of hours.
//hours = totalSeconds / 3600;
//BigDecimal bdHours = new BigDecimal( Double.toString( hours ) );
//
//// The minutes are the remainder that's left after getting the hours. Since
//// there are 60 seconds in one minute divide that remainder by 60.
//minutes = ( totalSeconds % 3600 ) / 60;
//BigDecimal bdMinutes = new BigDecimal( Double.toString( minutes ) );
//
//// The seconds are what's left over after getting the hours and minutes.
//seconds = ( totalSeconds % 3600 ) - ( minutes * 60 );
//BigDecimal bdSeconds = new BigDecimal( Double.toString( seconds ) );

// System.out.println( "\nA 56K modem will take " + bdHours + " hours, " + bdMinutes + " minutes, and " + bdSeconds + " seconds." );
// System.out.print( "\nContinue?(y/n): " );
// choice = sc.next();

System.out.println( "\nA 56K modem will take " + hours + " hours, " + minutes + " minutes, and " + seconds + " seconds." );
System.out.print( "\nContinue?(y/n): " );
choice = sc.next();

}
while ( choice.equalsIgnoreCase( "y" ) );
}
}

I think that I am loosing something when I do the division for totalSeconds. I should point out that when I used a an int value such as 4206 seconds instead of doing a calculation I get the correct answer(1 hour, 10 mins 6 secs)

KP>

[K Parsons]

I forgot to add that in the book it shows the result for a 50MB file as 2 hours 44 minutes and 6 seconds. I got the 2 and 44 but I'm getting 0 seconds.

KP>

[Campbell Ritchie]

You have correctly calculated the minutes with % 3600. Have you tried the same sort of thing for seconds?

[K Parsons]

The formula I have works. If I use the example of 4206 seconds instead of reading a value in and doing a division it works out the following way:

(1) There are 3600 seconds in one hour so divide by 3600.

4206 / 3600 = 1 ->This is the number of hours

4206 % 3600 = 606 -> This is the remainder from the division


(2) There are 60 seconds in one minute so divide 606 by 60 to get the minutes

606 / 60 = 10 -> This is the number of minutes

606 % 60 = 6 -> This remainder is the number of seconds.


(3) To get the number of seconds I used the following formula:

(4206 % 3600) - (60 * 10)

(totalNumberOfSeconds % secondsPerHour) - (secondsPerMinute * minutes)

KP>

[K Parsons]

Problem Solved! The solution is to cast the result of division to a long. You can also use the Math.round method.

KP>