» AWT/Swing: Uhr flackert

import java.awt.BasicStroke;
import java.awt.Canvas;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.geom.Line2D;
import java.util.Calendar;
import java.util.GregorianCalendar;
import java.util.Timer;
import java.util.TimerTask;

import javax.swing.JFrame;
import javax.swing.SwingUtilities;

public class Uhr extends JFrame {
	private static final long serialVersionUID = 1L;

	private Canvas canvas = new Canvas() {
		private static final long serialVersionUID = 1L;

		private void smallLine(Graphics2D g2d, int x0, int y0, int x1, int y1) {
			g2d.setStroke(new BasicStroke(5f));
			g2d.draw(new Line2D.Double(x0, y0, x1, y1));
		}

		private void bigLine(Graphics2D g2d, int x0, int y0, int x1, int y1) {
			g2d.setStroke(new BasicStroke(10f));
			g2d.draw(new Line2D.Double(x0, y0, x1, y1));
		}

		@Override
		public void paint(Graphics g) {
			Graphics2D g2d = (Graphics2D) g;
			int w = this.getWidth();
			int h = this.getHeight();
			int wh = Math.min(w, h);
			int wh2 = wh / 2;
			g2d.drawOval(5, 5, wh - 10, wh - 10);
			for (int i = 0; i < 12; i++) {
				int x0 = (int) (wh2 + (wh2 - 20) * Math.cos(Math.toRadians(360 / 12 * i)));
				int y0 = (int) (wh2 + (wh2 - 20) * Math.sin(Math.toRadians(360 / 12 * i)));
				int x1 = (int) (wh2 + (wh2 - 10) * Math.cos(Math.toRadians(360 / 12 * i)));
				int y1 = (int) (wh2 + (wh2 - 10) * Math.sin(Math.toRadians(360 / 12 * i)));
				smallLine(g2d, x0, y0, x1, y1);
			}
			{
				// Calibrate
				Calendar calendar = GregorianCalendar.getInstance();
				float minute = calendar.get(Calendar.MINUTE);
				float hour = calendar.get(Calendar.HOUR) + (minute / 60f); // The hour pointer should tick every minute.
				minute += calendar.get(Calendar.SECOND) / 60f; // The minute pointer should tick every second.

				// Draw, wh2 is the center
				int x0 = (int) (wh2 + (wh2 - 20) * Math.cos(Math.toRadians(360 / 60 * minute - 90)));
				int y0 = (int) (wh2 + (wh2 - 20) * Math.sin(Math.toRadians(360 / 60 * minute - 90)));
				int x1 = (int) (wh2 + (wh2 - 40) * Math.cos(Math.toRadians(360 / 12 * hour - 90)));
				int y1 = (int) (wh2 + (wh2 - 40) * Math.sin(Math.toRadians(360 / 12 * hour - 90)));
				smallLine(g2d, wh2, wh2, x0, y0);
				bigLine(g2d, wh2, wh2, x1, y1);
			}
		}
	};

	public Uhr() {
		add(canvas);
		setSize(400, 400);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setVisible(true);

		// Repaint every second.
		new Timer().schedule(new TimerTask() {
			@Override
			public void run() {
				SwingUtilities.invokeLater(new Runnable() {
					@Override
					public void run() {
						canvas.repaint();
					}
				});
			}
		}, 1000, 1000);
	}

	public static void main(String[] args) {
		new Uhr();
	}
}

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