Mean&Variance

package meanvariance;
import javax.swing.JOptionPane;
public class MeanVariance
{
public static void main (String[] args)
{
int i=0,n,sum1=0,sum2=0;
//設定在迴圈外面，否則出了迴圈定義就不見了
double e=0;
String number=JOptionPane.showInputDialog("Please enter a number.");
n= Integer.parseInt(number);
while(n>=0)
{
sum1+=n;
e=n*n;
sum2+=e;
i++;
n=0;
number=JOptionPane.showInputDialog("Please enter a number.");
n= Integer.parseInt(number);
}
if (sum1<0)
System.out.println("Mean =0\nVariance=0\n");
else
{
double mean=sum1/i;
double variance=sum2-mean*mean;
System.out.println("Mean="+mean+"\nVariance="+variance+"\n");
}
System.exit(0);
}
}