JAVA - Rotating Object moving with its Satelitte

 

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package test3;

import java.awt.Dimension;

import java.awt.Graphics;

import java.awt.Graphics2D;

import java.awt.Point;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.awt.geom.AffineTransform;

import javax.swing.JFrame;

import javax.swing.JPanel;

import javax.swing.SwingUtilities;

import javax.swing.Timer;

public class Test3 {

    public static void main(String[] args) {

        new Test3();

    }

    public Test3() {

        SwingUtilities.invokeLater(new Runnable() {

            @Override

            public void run() {

                JFrame frame = new JFrame();

                frame.add(new TestPane());

                frame.pack();

                frame.setLocationRelativeTo(null);

                frame.setVisible(true);

            }

        });

    }

    public class TestPane extends JPanel {

        private double angle;

        private double orbitAngle;

        private int xPos = 0;

        private int size = 20;

        private int outterRadius = size * 2;

        private int delta = 2;

        public TestPane() {

            new Timer(40, new ActionListener() {

                @Override

                public void actionPerformed(ActionEvent e) {

                    xPos += delta;

                    if (xPos + size >= getWidth()) {

                        xPos = getWidth() - size;

                        delta *= -1;

                    } else if (xPos < 0) {

                        xPos = 0;

                        delta *= -1;

                    }

                    angle += 4;

                    orbitAngle -= 2;

                    repaint();

                }

            }).start();

        }

        @Override

        public Dimension getPreferredSize() {

            return new Dimension(400, 200);

        }

        protected Point pointOnCircle() {

            double rads = Math.toRadians(orbitAngle - 180); // Make 0 point out to the right...

            int fullLength = Math.round((outterRadius));

            // Calculate the outter point of the line

            int xPosy = Math.round((float) (Math.cos(rads) * fullLength));

            int yPosy = Math.round((float) (Math.sin(rads) * fullLength));

            return new Point(xPosy, yPosy);

        }

        @Override

        protected void paintComponent(Graphics g) {

            super.paintComponent(g);

            Graphics2D g2d = (Graphics2D) g.create();

            int yPos = (getHeight() - size) / 2;

            // Transform the offset

            g2d.transform(AffineTransform.getTranslateInstance(xPos, yPos));

            Graphics2D earthG = (Graphics2D) g2d.create();

            // Rotate around the 0x0 point, this becomes the center point

            earthG.transform(AffineTransform.getRotateInstance(Math.toRadians(angle)));

            // Draw the "earth" around the center point

            earthG.drawRect(-(size / 2), -(size / 2), size, size);

            earthG.dispose();

            // Removes the last transformation

            Graphics2D moonG = (Graphics2D) g2d.create();            

            // Calclate the point on the circle - based on the outterRadius or

            // distance from the center point of the earth

            Point poc = pointOnCircle();

            int moonSize = size / 2;

            // This is only a visial guide used to show the position of the earth

            //moonG.drawOval(-outterRadius, -outterRadius, outterRadius * 2, outterRadius * 2);

            moonG.fillOval(poc.x - (moonSize / 2), poc.y - (moonSize / 2), moonSize, moonSize);

            moonG.dispose();

            g2d.dispose();

        }

    }

}