public void actionPerformed(ActionEvent e) {
if (e.getSource() == clearButton) {
history.clear();
canvas.init();
canvas.repaint();
} else if (e.getSource() == redButton) {
Command cmd = new ColorCommand(canvas, Color.red);
history.append(cmd);
cmd.execute();
} else if (e.getSource() == greenButton) {
Command cmd = new ColorCommand(canvas, Color.green);
history.append(cmd);
cmd.execute();
} else if (e.getSource() == blueButton) {
Command cmd = new ColorCommand(canvas, Color.blue);
history.append(cmd);
cmd.execute();
} else if (e.getSource() == undoButton) {
history.undo();
canvas.repaint();
}
}
public void mouseDragged(MouseEvent e) {
Command cmd = new DrawCommand(canvas, e.getPoint());
history.append(cmd);
cmd.execute();
}