Make button the width of 2 columns

Question

In my java code below I am trying to figure out how to stretch a button the width of 2 columns. You can see in the photo below what I am trying to do. I am not sure if this is something that requires the use of constraints or other proprieties. Possibly somehow you could make the columns width larger I am guessing or you can do something with the grid layout library in java.

import java.awt.*;
import javax.swing.*;

public class safe {
    
    private JFrame frame2;
    private JPanel panel2;
    
    private JLabel nameLabel2 ;
    private TextField nameTextfield2;
    
    private JLabel emailLabel2 ;
    private TextField emailTextfield2;
    
    public safe() {
        JButton button = new JButton("SUBMIT");
        
        nameTextfield2 = new TextField();
        emailTextfield2 = new TextField();

        nameLabel2 = new JLabel("name");
        emailLabel2 = new JLabel("Email");

        JFrame frame = new JFrame();
        JPanel panel = new JPanel();

        panel.setBorder(BorderFactory.createEmptyBorder(300, 300, 150, 150));
        panel.setLayout(new GridLayout(3,1));
        panel.add(nameLabel2);
        panel.add(nameTextfield2);
    
        panel.add(emailLabel2);
        panel.add(emailTextfield2);

        panel.add(button);

        frame.add(panel,BorderLayout.CENTER);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setTitle("Our Gui");
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        new safe();
    }
}