在鼠标点击上生长分形树

Question

如何在每次按下JButton时使分形树生长？我想让它看起来每次点击按钮时分支更多。

我目前有这个绘制分形树的代码。

import java.awt.BasicStroke;
import java.awt.Graphics2D;
import java.awt.Stroke;
import java.awt.geom.*;

public class Tree {
    public float posX = 0;
    public float posY = 0;

    public void Tree(){

    }

    public void branch(Graphics2D g2, float len) {
        g2.setStroke(new BasicStroke(2));

        g2.draw(new Line2D.Float(posX, posY, 0, -len)); // Draw the branch itself

        g2.translate(0, -len); // Move to the end of that line

        len *= 0.66; // Shrink the length of the branch

        if (len > 2) { // Base case: exit when the length of the branch is 2
                        // pixels or less
            AffineTransform at = g2.getTransform();
            g2.rotate(Math.PI / 5); // Rotate to the right
            branch(g2, len); // Call itself to draw two shorter branches
            g2.setTransform(at);

            // Repeat the same thing
            at = g2.getTransform();
            g2.rotate(-Math.PI / 5);
            branch(g2, len);
            g2.setTransform(at);
        }
    }
}

我还有一个Panel类，它显示了花园环境中的树（不包括花园类）

import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;



public class Panel extends JPanel implements ActionListener  {

    public static final int WINDOW_W = 1280;
    public static final int WINDOW_H = 720;

    private JButton simpleGarden;

    private Text txt;
    Tree tree;

    Garden garden;

    public Panel(){
        this.setBackground(Color.GRAY);
        setPreferredSize(new Dimension(WINDOW_W, WINDOW_H));
        setLayout(new FlowLayout());

        simpleGarden = new JButton("START YOUR GARDEN");
        add(simpleGarden);
        simpleGarden.addActionListener(this);

        txt = new Text();

    }

    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D) g;

        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        if (garden != null){
            garden.showGarden(g2);
            g2.setColor(new Color(139,69,19));
            g2.translate(WINDOW_W/2, WINDOW_H - 75);
            tree.branch(g2, 120); // display fractal
            txt.removeText(g2);
            }
        else{
            txt.startGarden(g2);
        }

    }

    @Override
    public void actionPerformed(ActionEvent e) {

        if (e.getActionCommand() == "START YOUR GARDEN") {
            garden = new SimpleGarden();
            tree = new Tree();

            remove(simpleGarden);
        }



        repaint();

    }

}