How can i make a workbook in java which accepts dynamic values of string in java?

Its a simple program where i have a text field and i get user input .
i store it in a global variable and create a function to get the file path for the workbook.
however i am made to change it to static and all my files created are named null.
i am using eclipse IDE and apache poi version. 5.0.0.

// imported files
public class MyFrame extends JFrame implements ActionListener{
String name;
JButton button;
JTextField textField;
String workbook1() {
String name1="D:\\"+name+".xlsx";
return name1;
}
MyFrame(){
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
this.setLayout(new FlowLayout());
button = new JButton("Submit");
button.addActionListener(this);
textField = new JTextField();
textField.setPreferredSize(new Dimension(250,40));
textField.setFont(new Font("Consolas",Font.PLAIN,35));
textField.setForeground(new Color(0x00FF00));
textField.setBackground(Color.black);
textField.setCaretColor(Color.white);
textField.setText("username");
this.add(button);
this.add(textField);
this.pack();
this.setVisible(true);
}
@Override
public void actionPerformed(ActionEvent e) {
if(e.getSource()==button) {
System.out.println("Welcome "+ textField.getText());
name=textField.getText();
//button.setEnabled(false);
//textField.setEditable(false);
}
}
public static void main(String args[]) throws IOException {
new MyFrame();
Workbook wb = new XSSFWorkbook();
Sheet sheet1 = wb.createSheet("Ripon");
FileOutputStream fileOut = new FileOutputStream(workbook1());
wb.write(fileOut);
fileOut.close();
wb.close();
}
}

I am just a beginner and any help is appreciated. The code is stolen from BroCode and Stack overflow

I am trying to create a java application where i can enter details into different columns and rows to create a kind of bill.
I watch tutorial and customize it to my need.

I got the answer to my question: instead of creating a new global variable I should have made a new form in the actionPerformed method.

mainbutton.setText("SUBMIT");
mainbutton.setPreferredSize(new Dimension(100,25));
maintext.setPreferredSize(new Dimension(100,25));
mainbutton.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == mainbutton) {
            try {
                XSSFWorkbook workbook = new XSSFWorkbook();
                Sheet sheet = workbook.createSheet("Data");
                FileOutputStream fileOutputStream = new FileOutputStream(".\\documents\\"+maintext.getText() + ".xlsx");
                workbook.write(fileOutputStream);
                fileOutputStream.close();
                System.out.println("Workbook saved to file: " + maintext + ".xlsx");
                maintext.setEditable(false);
                mainbutton.setEnabled(false);
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }
    }
});

//adding stuff to the main frame	
mainframe.add(mainlabelheading,BorderLayout.NORTH);
mainframe.add(mainlabelheading2,BorderLayout.CENTER);
mainframe.add(mainlabelheadingempty,BorderLayout.SOUTH);
gbc.gridx=0;
gbc.gridy=0;
mainlabelheading2.add(mainlabelheading2sublabel1,gbc);
gbc.gridx=2;
gbc.gridy=0;
mainlabelheading2.add(mainbutton,gbc);
gbc.gridx=1;
gbc.gridy=0;
mainlabelheading2.add(maintext,gbc);

Did play with the code and found out I was referencing a non static variable from a static method. When I changed the global variable to static it was creating null .xlsx files. Then used ChatGPT and stackoverflow to find the answer for my solutions.