Net Beans Program to Find Factorial of A number

private void CalculateActionPerformed(java.awt.event.ActionEvent evt)
{                                         
       
        double N= Double.parseDouble(t1.getText());
        double F=1;
       
                  for(double i=N; i>=1;i--)
                          {
                                    F=F*i;
                          }  
                 r.setText("FaCtOrial = "+" "+ F);
       
            if (N==0)
            r.setText("Factorial = "+" "+"1");
}