java notebook save button

I develop a notebook/text editor and i want to make a save button. My problem is that the most solutions develop a “Save as” button but I want just a save button. To be more clear, I want to write things to my editor then pressing save and when I open my editor the text will appear. If someone knows how to make this thing then I would really appreciate!
Here is my code:

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
import java.io.*;

public class Gui extends JFrame implements ActionListener {

    private static final long serialVersionUID = 1L;
    private JPanel panel = new JPanel();
    private JPanel mainPanel= new JPanel();
    private JPanel otherPanel = new JPanel();

    private TextArea text = new TextArea("", 44, 180,
            TextArea.SCROLLBARS_VERTICAL_ONLY);

    private JButton saveButton;

    GridLayout gridLayout = new GridLayout();

    public Gui() {

        this.setTitle("Notebook");

        setDefaultCloseOperation(EXIT_ON_CLOSE);

        this.getContentPane().setLayout(new BorderLayout());
        this.getContentPane().add(panel);

        panel.add(mainPanel, BorderLayout.CENTER);
        panel.add(otherPanel, BorderLayout.NORTH);

        mainPanel.setLayout(new GridLayout(1, 1));
        otherPanel.setLayout(new GridLayout(1, 2));

        saveButton = new JButton("Save");
        saveButton.addActionListener(this);

        mainPanel.add(text);

        otherPanel.add(saveButton);

    }

    @Override
    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == saveButton) {

            try {
                            // this create a NEW file named note.txt
                File file = new File("note.txt");
                FileWriter out = new FileWriter(file);
                out.write(text.getText());
                out.close();
            } catch (FileNotFoundException e2) {
                e2.printStackTrace();
            } catch (IOException e3) {
                e3.printStackTrace();
            }
        }
    }
}