int val = (int) textFieldGen.getModel().getValue(); //getting the value from JSpinner

JTextField[] txtField = new JTextField[val];

//tried panel.revalidate(); panel.repaint();

//removing elements if exists.  gives null pointer exception.

try {
     for (JTextField txtComp : txtField) {
       panel.remove(txtComp);
    }
} catch (Exception ex) {
        System.out.println(ex);
}

panel.revalidate();
panel.repaint();


//creating
int row = 1;
for (int i = 0; i < txtField.length; i++) {
    row++;
    layout.appendRow(RowSpec.decode("30px"));
    txtField[i] = new JTextField(10);
    panel.add(txt[i], cc.xy(4, row));
}
panel.revalidate();
panel.repaint();

public JPanel createPanel(int numberOfTextFields) {
    JPanel panel=new JPanel(new ...);//create new panel

    JTextField tfs[]=new JTextField[numberOfTextFields];//create array of textFields

    for(int i=0;i<numberOfTextFields;i++) {
        tfs[i]=new JTextField();//create the textfield
        panel.add(tfs[i]...);//add it to the panel
    }

    return panel;
}