No space between buttons

Question

Hi,
Here i put three buttons on panel one under one but there is no space between them although i determine the space ..
my code :
import java.awt.Color;
import java.awt.Dimension;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class MainFram extends JFrame {
    private JPanel mainPanel;
    private JButton[] buttons;
//    private JLabel[] labels;
    private String[] labelNames = {"Levels", "Help", "About"};
    private static final int BUTTON_DISTANCE_Y = 20;
    private static final int BUTTON_WIDTH = 50, BUTTON_HEIGHT = 50;
    public MainFram() {
        intializingPanel();
        intializingButtons();
      //  intializingLabel();
        getContentPane().add(mainPanel);
    public static void main(String[] args) {
        MainFram mainFram = new MainFram();
        mainFram.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        mainFram.setSize(new Dimension(600, 300));
        mainFram.setLocationRelativeTo(null);
        mainFram.setVisible(true);
        mainFram.setExtendedState(MAXIMIZED_BOTH);
    private void intializingPanel() {
        mainPanel = new JPanel(null);
        mainPanel.setBounds(100, 10, 600, 300);
        mainPanel.setBorder(BorderFactory.createLineBorder(Color.BLACK, 5));
        mainPanel.setBackground(Color.GREEN);
    private void intializingButtons() {
        buttons = new JButton[labelNames.length];
        for (int i = 0; i < labelNames.length; ++i) {
            buttons[i] = new JButton();
            buttons.setBounds(50, (BUTTON_DISTANCE_Y * i) + 50, BUTTON_WIDTH, BUTTON_HEIGHT);
mainPanel.add(buttons[i]);
// private void intializingLabel() {
Why this ???
thanks in advance                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               

Answer 1

beshoyatefw wrote:
Why this ???Because you have the equation wrong!
   buttons.setBounds(50, ((BUTTON_DISTANCE_Y + BUTTON_WIDTH) * i) + 50, BUTTON_WIDTH, BUTTON_HEIGHT);