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

import static java.awt.GridBagConstraints.BOTH;

public class GridBagLayoutExample {

    public static void main(String[] args) {

        JFrame frame = new JFrame();

        // GridBagLayout is layout manager which will place components
        // in grid (table)
        GridBagLayout layoutManager = new GridBagLayout();

        // Set the layout manager for the container
        // The same method works also for JPanel
        frame.setLayout(layoutManager);

        // GridBagConstraints defines how the component will be positioned
        // in the container. The components will be placed in grid (table).
        GridBagConstraints c = new GridBagConstraints();
        c.weighty = 1;          // How to distribute extra vertical space
        c.weightx = 1;          // How to distribute extra horizontal space
        c.fill = BOTH;          // When the container is being resized, resize
                                // both width and height of this component

        c.gridy = 0;            // The component will be placed in first row
        c.gridwidth = 4;        // The component will occupy four cells horizontally

        frame.add(new JTextField(), c);

        c.gridwidth = 1;
        c.gridy = 1;
        frame.add(new JButton("1"), c);
        frame.add(new JButton("2"), c);
        frame.add(new JButton("3"), c);
        frame.add(new JButton("4"), c);

        c.gridy = 2;
        frame.add(new JButton("5"), c);
        frame.add(new JButton("6"), c);
        frame.add(new JButton("7"), c);
        frame.add(new JButton("8"), c);

        frame.pack();
        frame.setVisible(true);
    }
}