递归画三角形 ---  先画该三角，然后求三条边的中点，递归画三个小三角形。

运行结果：

代码：

package shiyan6;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Point;
import javax.swing.JPanel;
public class Triangle extends JPanel{
	private int n=0;
	public void run(){
		n++;
		repaint();
	}
	protected void paintComponent(Graphics g){
		g.setColor(Color.red);
		super.paintComponent(g);
		Point p1 = new Point(50,500);
		Point p2 = new Point(550,500);
		Point p3 = new Point(300,67);
		display(g,n,p1,p2,p3);
	}
	private void display(Graphics g,int n,Point p1,Point p2,Point p3){
		if (n>0){
			g.drawLine(p1.x, p1.y, p2.x, p2.y);
			g.drawLine(p1.x, p1.y, p3.x, p3.y);
			g.drawLine(p3.x, p3.y, p2.x, p2.y);
			Point p4 = getmid(p1,p2);
			Point p5 = getmid(p1,p3);
			Point p6 = getmid(p2,p3);
			display(g,n-1,p1,p4,p5);
			display(g,n-1,p2,p4,p6);
			display(g,n-1,p3,p6,p5);
		}
	}
	private Point getmid(Point p1,Point p2){
		Point p = new Point();
		p.x=(p1.x+p2.x)/2;
		p.y=(p1.y+p2.y)/2;
		return p;
	}
}

package shiyan6;
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
public class abcd extends JFrame{
	
	private Triangle T = new Triangle();
	private JButton jb = new JButton("Increase");
	
	public abcd(){
		this.add(T);
		JPanel panel=new JPanel();
		panel.add(jb);
		this.add(panel,BorderLayout.SOUTH);
		jb.addActionListener(new ActionListener(){
			public void actionPerformed(ActionEvent e){
				T.run();
			}
		});
	}
	public static void main(String[] args) {
		abcd f = new abcd();
		f.setTitle("思瑞平斯基三角");
		f.setSize(600,600);
		f.setLocationRelativeTo(null);
		f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		f.setVisible(true);
	}
}