private void inchButtonActionPerformed(java.awt.event.ActionEvent evt) {                                           
        String s = inchField.getText();
        try {
            double inch = Double.parseDouble(s);
            inch = inch*100;
            int inch2 = (int)inch;

            cmField.setText(""+Harjoitus2.inchesToCm(inch));
        } catch (NumberFormatException ex) {
            JOptionPane.showMessageDialog(this, "You must input a number",
                    "Invalid input", JOptionPane.ERROR_MESSAGE);
        }
    }