Nick Dunn

package circle;

import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JComponent;
import javax.swing.JFrame;

/**
 * Alternate way of drawing previous example, using rotations rather than
 * manually calculating x and y positions
 * @author Nick
 */
public class RotatedCircle extends JComponent {

    private static final int NUM_DOTS = 20;
    private static final int SIZE = 200;
    private static final double RADIANS_PER_DOT = 2.0 * Math.PI / NUM_DOTS;

    public RotatedCircle() {
        super();
        setPreferredSize(new Dimension(SIZE, SIZE));
    }

    /**
     * Draw a series of dots in a circular pattern
     * @param g
     */
    @Override
    public void paintComponent(Graphics g) {
        Graphics2D g2 = (Graphics2D) g;
        // Don't forget to call the super method
        super.paintComponent(g);

        int radius = getWidth()/3;

        // Translate the origin to the center of window
        g2.translate(getWidth() /2, getHeight() /2);
        for (int i = 0; i < NUM_DOTS; i++) {
            g2.rotate(RADIANS_PER_DOT);
            // We have rotated about the origin; draw a ray out along x axis
            // of new coordinate system
            g2.drawOval(radius, 0, 1, 1);

        }

    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("Rotated circle");
        frame.add(new RotatedCircle());
        frame.pack();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }

}