java GUI layout test

LayoutTest.java

import java.awt.BorderLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTable;

public class LayoutTest extends JFrame{
	public static final int x_start = 150, y_start = 100;
	public static final int WIDTH = 500, HEIGHT = 150;

	public LayoutTest(){
		super("My title");
		setBounds(x_start, y_start, WIDTH, HEIGHT);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		
		setLayout(new BorderLayout());
		
		int button_num = 5;
		
		// ==== set button ====
		JButton [] headButton = new JButton[button_num];
		for(int i=1;i<=button_num;i++)
			headButton[i-1] = new JButton("button" + i);

		JPanel headPanel = new JPanel();

		for(int i=0;i<button_num;i++)
			headPanel.add(headButton[i]);

		add(headPanel,BorderLayout.NORTH);
		
		// ==== set table ====
		int row = 3, col = 4;
		String [][] data = new String[row][col];
		for(int i=0;i<row;i++)
			for(int j=0;j<col;j++)
				data[i][j] = "(" + i + ", " + j + ")" ;

		String [] head = new String[col];
		for(int i=0;i<col;i++)
			head[i] = "head" + i;

		JTable table=new JTable(data,head);
		
		// ==== set layout for table ====
		JPanel tabPanel = new JPanel(new BorderLayout());
		tabPanel.add(table.getTableHeader(),BorderLayout.NORTH);
		tabPanel.add(table,BorderLayout.CENTER);
		
		JPanel test = new JPanel();
		test.add(tabPanel);
		
		add(test,BorderLayout.CENTER);
	}

	public static void main(String[] args) {
		LayoutTest window = new LayoutTest();
		window.setVisible(true);
	}
}