Stiv i Java, simpel klasse interaktion

Jeg har to filer, den ene indeholder en klasse der kan regne downloadshastighed ud. Det skal test-filen så printe ud, men jeg har lidt problemer.

test.java:
public class test
{
        public static void main(String[] arg)
        {
                downloadSpeed a = new downloadSpeed(123, 123);

                System.out.println("Test" + a.time['0']);

        }
}

downloadSpeed.java:
import java.math.*;

public class downloadSpeed
{
        public double usr_kbit;        // Users connection to the net in KB/s
        public double chars_pr_secs;    // How many chars that can be transferred pr. second
        public double file_size;        // The size of the file the user wants to download
        public double seconds;          // How many seconds, is used temporarely to calculate the other values
        public double time[];

        downloadSpeed(double speed, double size)
        {
                usr_kbit = speed;
                file_size = size;

                chars_pr_secs = usr_kbit * 1024.0;      // Calculate how many characters the user can download in seconds
                file_size = Math.floor(file_size * 1024.0 * 1024.0); // Calculate how much bytes the download is

                double time[] = new double[3];
                seconds = file_size / chars_pr_secs;
                time[0] = Math.floor(seconds / 3600.0); // hours
                seconds = seconds - time[0] * 3600.0;
                time[1] = Math.floor(seconds / 60.0);  // minutes
                time[2] = seconds - time[1] * 60.0;    // seconds
        }
        public void output()
        {
            //Virkede egentligt ikke selvom jeg forventede det ville virke, nogen der vil give noget info heromkring?
            //System.out.println("TID: " + this.time[0] + " hours, " + this.time[1] + " minutes, " + this.time[2] + " sekunder.");
                //return time;
        }
}

Fejlen er:
me@you ~/java $ java test
Exception in thread "main" java.lang.NullPointerException
        at test.main(test.java:8)