Correction

public class Factorielle
{
public static void main(String[] args)
{
Scanner sc = new Scanner(System.in);
System.out.println("Entrez un nombre n :");
int n = sc.nextInt();
int a=n-1;

int r=0;
r=n*a;
int result;

if (n<=0)
{
r=1;
}
else
{
while(a>1)
{
a=a-1;
result=r*a;
}
}
System.out.print("Le produit factoriel de "+n+" est : "+result);
}
}