Swing/AnalogClock のバックアップ(No.1)

JPanel clock = new JPanel() {
  @Override protected void paintComponent(Graphics g) {
    Graphics2D g2 = (Graphics2D) g.create();
    g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                        RenderingHints.VALUE_ANTIALIAS_ON);
    Rectangle rect = SwingUtilities.calculateInnerArea(this, null);
    g2.setColor(Color.BLACK);
    g2.fill(rect);
    g2.setColor(Color.WHITE);
    g2.translate(rect.getCenterX(), rect.getCenterY());
    float radius = Math.min(rect.width, rect.height) / 2f - 10f;

    // Drawing the hour markers
    float hourMarkerLen = radius / 6f - 10f;
    Shape hourMarker = new Line2D.Float(0f, hourMarkerLen - radius, 0f, -radius);
    AffineTransform at = AffineTransform.getRotateInstance(0d);
    for (int i = 0; i < 12; i++) {
      at.rotate(Math.PI / 6d);
      g2.draw(at.createTransformedShape(hourMarker));
    }

    // Drawing the minute hand
    float minuteHandLen = 5f * radius / 6f;
    Shape minuteHand = new Line2D.Float(0f, 0f, 0f, -minuteHandLen);
    AffineTransform at2 = AffineTransform.getRotateInstance(
        time.getMinute() * Math.PI / 30d);
    g2.setStroke(new BasicStroke(4f));
    g2.setPaint(Color.WHITE);
    g2.draw(at2.createTransformedShape(minuteHand));

    // Drawing the hour hand
    float hourHandLen = radius / 3f;
    Shape hourHand = new Line2D.Float(0f, 0f, 0f, -hourHandLen);
    AffineTransform at3 = AffineTransform.getRotateInstance(
        time.getHour() * Math.PI / 6d);
    g2.setStroke(new BasicStroke(8f));
    g2.draw(at3.createTransformedShape(hourHand));

    // Drawing the second hand
    float r = radius / 6f;
    float secondHandLen = radius - r;
    Shape secondHand = new Line2D.Float(0f, r, 0f, -secondHandLen);
    AffineTransform at1 = AffineTransform.getRotateInstance(
        time.getSecond() * Math.PI / 30d);
    g2.setPaint(Color.RED);
    g2.setStroke(new BasicStroke(1f));
    g2.draw(at1.createTransformedShape(secondHand));
    g2.fill(new Ellipse2D.Float(-r / 4f, -r / 4f, r / 2f, r / 2f));

    g2.dispose();
  }
};

new Timer(200, e -> {
  time = LocalTime.now(ZoneId.systemDefault());
  clock.repaint();
}).start();