Plz tell me the error at this simple program

Question

at this orogram i want the user to input the number and then he get th factorial...
my program is:
import javax.swing.JOptionPane;
public class Ch4_32a
public static void main (String[]args)
int f=1, i=1,N;
String E;
          String M = JOptionPane.showInputDialog("Enter the number");
          N=Integer.parseInt(M);
          while(i<=N);
               f=f*i;
               i++;
          JOptionPane.showMessageDialog(null,"the factorial is"+E);
          f=Integer.parseInt(E);
******and when i copile it the result is:
C:\Documents and Settings\F A M I L Y\Desktop\MyProgs\azza\Ch4_32a.java:22: variable E might not have been initialized
          JOptionPane.showMessageDialog(null,"the factorial is"+E);
^
1 error
it tell me to init the value of E but ir is a string,,
so plz help me to get the real error

Answer 1

i delete the (parseInt{) and compile it completle
but when i excut it the firs widow appear (Ent the number)
i Enter the number and then "ok" but the second window don't appear which well tell me the result({f)