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Task/Draw-a-clock/Java/draw-a-clock.java

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+import java.awt.*;
+import java.awt.event.*;
+import java.util.Calendar;
+import javax.swing.*;
+
+class Clock extends JPanel {
+
+    final float degrees06 = (float) Math.toRadians(6);
+    final float degrees30 = degrees06 * 5;
+    final float degrees90 = degrees30 * 3;
+
+    final int size = 550;
+    final int spacing = 20;
+    final int diameter = size - 2 * spacing;
+    final int x = diameter / 2 + spacing;
+    final int y = diameter / 2 + spacing;
+
+    public Clock() {
+        setPreferredSize(new Dimension(size, size));
+        setBackground(Color.white);
+
+        new Timer(1000, new ActionListener() {
+            @Override
+            public void actionPerformed(ActionEvent e) {
+                repaint();
+            }
+        }).start();
+    }
+
+    @Override
+    public void paintComponent(Graphics gg) {
+        super.paintComponent(gg);
+        Graphics2D g = (Graphics2D) gg;
+        g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
+                RenderingHints.VALUE_ANTIALIAS_ON);
+
+        g.setColor(Color.black);
+        g.drawOval(spacing, spacing, diameter, diameter);
+
+        Calendar date = Calendar.getInstance();
+        int hours = date.get(Calendar.HOUR);
+        int minutes = date.get(Calendar.MINUTE);
+        int seconds = date.get(Calendar.SECOND);
+
+        float angle = degrees90 - (degrees06 * seconds);
+        drawHand(g, angle, diameter / 2 - 30, Color.red);
+
+        float minsecs = (minutes + seconds / 60.0F);
+        angle = degrees90 - (degrees06 * minsecs);
+        drawHand(g, angle, diameter / 3 + 10, Color.black);
+
+        float hourmins = (hours + minsecs / 60.0F);
+        angle = degrees90 - (degrees30 * hourmins);
+        drawHand(g, angle, diameter / 4 + 10, Color.black);
+    }
+
+    private void drawHand(Graphics2D g, float angle, int radius, Color color) {
+        int x2 = x + (int) (radius * Math.cos(angle));
+        int y2 = y + (int) (radius * Math.sin(-angle)); // flip y-axis
+        g.setColor(color);
+        g.drawLine(x, y, x2, y2);
+    }
+
+    public static void main(String[] args) {
+        SwingUtilities.invokeLater(new Runnable() {
+            @Override
+            public void run() {
+                JFrame f = new JFrame();
+                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+                f.setTitle("Clock");
+                f.setResizable(false);
+                f.add(new Clock(), BorderLayout.CENTER);
+                f.pack();
+                f.setLocationRelativeTo(null);
+                f.setVisible(true);
+            }
+        });
+    }
+}