import java.awt.*;
import javax.swing.*;
public class Main{
    public static void main(String[] args){
        JFrame fr = new JFrame("test");
        MyPanel p1 = new MyPanel();
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.insets = new Insets(5, 5, 5, 5);
        gbc.fill = GridBagConstraints.HORIZONTAL;
        p1.setLayout(new GridBagLayout());
        gbc.gridx = 0;
        gbc.gridy = 0;
        p1.add(new JButton("btn1"), gbc);
        gbc.gridx = 1;
        gbc.gridy = 0;
        p1.add(new JButton("btn1"), gbc);
        gbc.gridx = 2;
        gbc.gridy = 0;
        p1.add(new JButton("btn1"), gbc);
        gbc.gridx = 0;
        gbc.gridy = 1;
        gbc.gridwidth = 2;
        p1.add(new JButton("btn2"), gbc);
        gbc.gridwidth = 1;
        gbc.gridx = 0;
        gbc.gridy = 2;
        p1.add(new JButton("btn3"), gbc);
        fr.setContentPane(p1);
        fr.setSize(500, 500);
        fr.setVisible(true);
        fr.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
}