Another update from ingydotnet^djgoku

Task/Sierpinski-carpet/Java/sierpinski-carpet-2.java

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+import java.awt.*;
+import java.awt.event.ActionEvent;
+import javax.swing.*;
+
+public class SierpinskiCarpet extends JPanel {
+    private final int dim = 513;
+    private final int margin = 20;
+
+    private int limit = dim;
+
+    public SierpinskiCarpet() {
+        setPreferredSize(new Dimension(dim + 2 * margin, dim + 2 * margin));
+        setBackground(Color.white);
+        setForeground(Color.orange);
+
+        new Timer(2000, (ActionEvent e) -> {
+            limit /= 3;
+            if (limit <= 3)
+                limit = dim;
+            repaint();
+        }).start();
+    }
+
+    void drawCarpet(Graphics2D g, int x, int y, int size) {
+        if (size < limit)
+            return;
+        size /= 3;
+        for (int i = 0; i < 9; i++) {
+            if (i == 4) {
+                g.fillRect(x + size, y + size, size, size);
+            } else {
+                drawCarpet(g, x + (i % 3) * size, y + (i / 3) * size, size);
+            }
+        }
+    }
+
+    @Override
+    public void paintComponent(Graphics gg) {
+        super.paintComponent(gg);
+        Graphics2D g = (Graphics2D) gg;
+        g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
+                RenderingHints.VALUE_ANTIALIAS_ON);
+        g.translate(margin, margin);
+        drawCarpet(g, 0, 0, dim);
+    }
+
+    public static void main(String[] args) {
+        SwingUtilities.invokeLater(() -> {
+            JFrame f = new JFrame();
+            f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+            f.setTitle("Sierpinski Carpet");
+            f.setResizable(false);
+            f.add(new SierpinskiCarpet(), BorderLayout.CENTER);
+            f.pack();
+            f.setLocationRelativeTo(null);
+            f.setVisible(true);
+        });
+    }
+}