Tree Painter winter 2020

package tree;

import java.awt.EventQueue;
import java.awt.Graphics;

import javax.swing.JFrame;
import java.awt.Toolkit;
import javax.swing.JLabel;
import java.awt.BorderLayout;
import javax.swing.JButton;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.UIManager;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class Main {

    private JFrame frmTreePainter;
    private JTextField textField;
    MyPanel panel_tree;
    private JLabel lblStatus;

    class MyPanel extends JPanel {
        int levels = 5;
        int minDistance = 5;

        void drawTree(Graphics g, int x, int y, int currentLevel) {
            if (currentLevel <= levels) {
                int distance = minDistance * (1 << (levels - currentLevel));
                g.drawOval(x, y, 10, 10);
                if (currentLevel < levels) {
                    g.drawLine(x, y, x - distance, y + 20);
                    g.drawLine(x, y, x + distance, y + 20);
                }
                drawTree(g, x - distance, y + 20, currentLevel + 1);
                drawTree(g, x + distance, y + 20, currentLevel + 1);
            }

        }

        @Override
        public void paint(Graphics g) {
            // TODO Auto-generated method stub
            super.paint(g);
            drawTree(g, getWidth() / 2, 10, 1);
        }

    }

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        try {
            UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
        } catch (Throwable e) {
            e.printStackTrace();
        }
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    Main window = new Main();
                    window.frmTreePainter.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the application.
     */
    public Main() {
        initialize();
    }

    /**
     * Initialize the contents of the frame.
     */
    void setLevel() {
        try {
            int depth = Integer.parseInt(textField.getText());
            panel_tree.levels = depth;
            panel_tree.repaint();
            lblStatus.setText("OK!");

        } catch (Exception e) {
            lblStatus.setText("Please enter an integer number!");
        }
    }
    private void initialize() {
        frmTreePainter = new JFrame();
        frmTreePainter.setIconImage(Toolkit.getDefaultToolkit()
                .getImage(Main.class.getResource("/com/sun/java/swing/plaf/windows/icons/ListView.gif")));
        frmTreePainter.setTitle("Tree painter GUI");
        frmTreePainter.setBounds(100, 100, 450, 300);
        frmTreePainter.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel panel = new JPanel();
        frmTreePainter.getContentPane().add(panel, BorderLayout.NORTH);

        JLabel lblDepth = new JLabel("Depth:");
        panel.add(lblDepth);

        textField = new JTextField();
        textField.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                setLevel();
            }
        });
        textField.setText("5");
        panel.add(textField);
        textField.setColumns(10);

        JButton btnPaint = new JButton("Paint!");
        btnPaint.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                setLevel();
            }
        });
        panel.add(btnPaint);

        panel_tree = new MyPanel();
        frmTreePainter.getContentPane().add(panel_tree, BorderLayout.CENTER);

        lblStatus = new JLabel(" ");
        frmTreePainter.getContentPane().add(lblStatus, BorderLayout.SOUTH);
    }

}