FractalTriangles.java

import java.awt.*;  // for graphics
import javax.swing.*;   // for JFrame

public class FractalTriangles {

    /**
    *   Program:    FractalTriangles.java
    *   Purpose:    Draw Sierpinski Triangle using recursive algorithm.
    *   Creator:    Chris Clarke
    *   Created:    03.04.2012
    *   Modified:   11.07.2013 larger size JFrame
    */

    public static void main(String[] args) {
        FractalTrianglesJFrame frame = new FractalTrianglesJFrame();
        frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

class FractalTrianglesJFrame extends JFrame {

    public FractalTrianglesJFrame() {
        setTitle("Fractal Triangles by Chris Clarke");
        // Set to maximum size.
        setSize(MAX_X, MAX_Y);
    }

    public void drawTriangle(Graphics g,int x0,int y0) {
        // draw filled-in triangle whose apex is at (x0, y0)

        for (int i=x0; i<=x0+2*TRI_HALF_BASE; i++)
            g.drawLine(i, y0+TRI_HEIGHT, x0+TRI_HALF_BASE, y0);

        // relatively long or short pause depending on value of DELAY
        for (int i=0; i<DELAY; i++);
    }

    public void draw3Triangles(Graphics g,int x0,int y0, int size) {
        // draw fractal using recursion

        size/=2;

        if (size==1) {
            // left corner
            drawTriangle(g, x0-TRI_HALF_BASE, y0+TRI_HEIGHT);
            // right corner
            drawTriangle(g, x0+TRI_HALF_BASE, y0+TRI_HEIGHT);
            // apex
            drawTriangle(g, x0, y0);
        } else { // recursive method call
            // left corner
            draw3Triangles(g, x0-size*TRI_HALF_BASE, y0+size*TRI_HEIGHT, size);
            // right corner
            draw3Triangles(g, x0+size*TRI_HALF_BASE, y0+size*TRI_HEIGHT, size);
            // apex
            draw3Triangles(g, x0, y0, size);
        }
    }

    public void paint(Graphics g) {
        // draw background
        g.setColor(new Color(100, 138, 255));
        g.fillRect(0,0,MAX_X,MAX_Y);
        // draw black triangles
        g.setColor(Color.BLACK);
        draw3Triangles(g, START_X, START_Y, SIZE);
    }

    public static final int MAX_X=1280;     // maximum width = width of screen
    public static final int MAX_Y=800;      // maximum height = height of screen
    public static final int START_X=MAX_X/2;
    public static final int START_Y=100;
    public static final int TRI_HEIGHT = 2;     // size in pixels of black triangle
    public static final int TRI_HALF_BASE = 2;  // size in pixels of black triangle
    public static final int DELAY=5000000;      // many iterations to slow down construction
    public static final int SIZE=256;       // size in pixels of base of largest triangle
}