Algoritmo Factorial En Java

import javax.swing.JOptionPane;

public class Factorial
{
private int x;
private int num;

public Factorial()
{
x=1;
num =0;
factorial();
}
public static void main (String args[])
{
Factorial x= new Factorial();
}
public void factorial()
{
num= Integer.parseInt(JOptionPane.showInputDialog("Digite el numero"));
for (int i=num;i>0; i--)
{
x=x*i;
}
JOptionPane.showMessageDialog(null,"El resultado es:"+x);
}
}