Topic: Java Programming

A Sierpinski Triangle is a fractal formed by drawing a triangle, and then using the midpoints of each side of triangle to form another triangle. This inner triangle is then removed. The result is three smaller triangles (one at the top and one in each corner) on which the process is repeated. After iteration N, the image will contain 3^N triangles, each of which is similar to the original triangle.

Task: Modify the following program so the maximum slider value changes, as appropriate, when the window is resized.

import javax.swing.*; import javax.swing.event.*; import java.awt.*; import java.util.*;

public class Driver extends JFrame implements ChangeListener{ private JSlider slider = new JSlider(JSlider.HORIZONTAL); private SierTriangle triangle = null; public Driver() { triangle = new SierTriangle(); triangle.setBackground(Color.WHITE); this.getContentPane().add(triangle, BorderLayout.CENTER); JPanel orderPanel = new JPanel(); orderPanel.add(new JLabel("Enter a Level: ")); orderPanel.add(slider); orderPanel.setBackground(Color.WHITE);

slider.setMaximum(10); slider.setMinimum(0); slider.setValue(0); Hashtable labels = new Hashtable(); labels.put(0, new JLabel("0")); labels.put(2, new JLabel("2")); labels.put(4, new JLabel("4")); labels.put(6, new JLabel("6")); labels.put(8, new JLabel("8")); labels.put(10, new JLabel("10")); slider.setMajorTickSpacing(1); slider.setLabelTable(labels); slider.setPaintTicks(true); slider.setSnapToTicks(true); slider.setPaintLabels(true); slider.addChangeListener(this); this.getContentPane().add(orderPanel, BorderLayout.SOUTH); this.setPreferredSize(new Dimension(750,750)); this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); this.pack(); this.setVisible(true); } public void stateChanged(ChangeEvent e) { triangle.setLevel(slider.getValue()); } @SuppressWarnings("unused") public static void main(String[] args) { Driver fr = new Driver(); } private class SierTriangle extends JPanel { private int level = 0; public void setLevel(int v) { level = v; repaint(); } public void paintComponent(Graphics g){ super.paintComponent(g); Point p1 = new Point(this.getWidth() / 2, 10); Point p2 = new Point(10, this.getHeight() - 10); Point p3 = new Point(this.getWidth() - 10, this.getHeight() - 10); displayTriangle(g, level, p1, p2, p3); } public Point midpoint (Point a, Point b){ Point mid = new Point(); mid.x = (a.x + b.x) / 2; mid.y = (a.y + b.y) / 2; return mid; } public void displayTriangle(Graphics g, int level, Point p1, Point p2, Point p3) { if (level == 0){ g.drawLine(p1.x, p1.y, p2.x, p2.y); g.drawLine(p1.x, p1.y, p3.x, p3.y); g.drawLine(p2.x, p2.y, p3.x, p3.y); }else{ Point p1_2 = midpoint(p1, p2); Point p2_3 = midpoint(p2, p3); Point p3_1 = midpoint(p3, p1);

displayTriangle(g, level - 1, p1, p1_2, p3_1); displayTriangle(g, level - 1, p1_2, p2, p2_3); displayTriangle(g, level - 1, p3_1, p2_3, p3); } } } }