How to change the co-ordinayte system?

Question

Hello to all,
I am working on a java project in which i want to display Earth's longitudes and latitudes. Right now my program giving me cartesian means the applet's own co-ordinate but i want the co-ordinates in degrees to solve some communication equations .
please help me to solve this problem.
I will be very thankfull to you all...
My code is given as:
import java.awt.*;
import java.applet.*;
import javax.swing.JApplet;
import javax.swing.JPanel;
import java.awt.event.*;
public class DrawEarth extends JApplet implements MouseListener
     public void mouseClicked (MouseEvent me) {
          xpos = me.getX();
            ypos = me.getY();
            // Check if the click was inside the Earth area.
            if ((xpos >50 && xpos < 450 && ypos >50 &&  ypos < 450)||(xpos >450 && xpos < 850 && ypos >50 &&  ypos < 450)) {
                 mouseClicked = true;
            // if it was not then mouseClicked is false;
            else
                 return ;
            repaint();
      public void mouseEntered (MouseEvent me) {}
      public void mousePressed (MouseEvent me) {}
      public void mouseReleased (MouseEvent me) {} 
      public void mouseExited (MouseEvent me) {}
     boolean mouseClicked;
     int  xpos,ypos;
     String msg;
    public void init() {
         //addMouseListener(this);
         super.init();
         addMouseListener(this);
        setContentPane(new JPanel() {
            final Dimension size = new Dimension(1000, 1000);
            final GradientPaint backgradient = new GradientPaint(0, 0, Color.WHITE, 0, 350, Color.BLACK);
            final GradientPaint earthgradient = new GradientPaint(0, 50, Color.CYAN, 0, 450, Color.GREEN);
            protected void paintComponent(Graphics g) {
                super.paintComponent(g);
                Graphics2D g2 = (Graphics2D) g;
                g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
                g2.setPaint(backgradient);
                g2.fillRect(0, 0, 1000, 1000);
                g2.setPaint(backgradient);
                g2.setPaint(earthgradient);
                g2.fillOval(50, 50, 400, 400);
                g2.fillOval(450, 50, 400, 400);
                g2.setColor(Color.BLUE);
                g2.setColor(Color.BLUE);
                g.drawString("270",35,250);
                g.drawString("300",70,250);
                g.drawString("330",145,250);
                  g.drawString("(0,0)",245,250);
                  g.drawString("30",345,250);
                  g.drawString("60",415,250);
                  g.drawString("90",445,250);
                  g.drawString("120",470,250);
                  g.drawString("150",545,250);
                     g.drawString("(180,0)",645,250);
                     g.drawString("210",745,250);
                     g.drawString("240",815,250);
                     g.drawString("270",850,250);
                     g.drawString("90",255,48);
                     g.drawString("60",255,77);
                     g.drawString("30",255,150);
                     g.drawString("-30",255,350);
                     g.drawString("-60",255,425);
                     g.drawString("-90",255,460);
                     g.drawString("90",650,48);
                     g.drawString("60",650,77);
                     g.drawString("30",650,150);
                     g.drawString("-30",650,350);
                     g.drawString("-60",650,425);
                     g.drawString("-90",650,460);
                for (int i = 0; i <= 180; i += 10) {
                    int widthlong = (int) (200 * Math.cos(Math.toRadians(i)));
                    g2.drawOval(250 - widthlong, 50, 2 * widthlong, 400);
                    g2.drawOval(650 - widthlong, 50, 2 * widthlong, 400);
                    int widthlat = (int) (200 * Math.sin(Math.toRadians(i)));
                    g2.drawLine(250 - widthlat, 250 - widthlong, 250 + widthlat, 250 - widthlong);
                    g2.drawLine(650 - widthlat, 250 - widthlong, 650 + widthlat, 250 - widthlong);
                double xco = xpos/22.22;
                double yco = ypos/22.22;
                    if(xpos >50 && xpos < 450 && ypos >50 && ypos < 250){
                         g.drawString("("+xpos+","+ypos+")",xpos,ypos);
                    if(xpos >450 && xpos < 850 && ypos >50 && ypos < 250){
                         g.drawString("("+xpos+","+ypos+")",xpos,ypos);
                    if(xpos >50 && xpos < 450 && ypos >250 && ypos < 450){
                         g.drawString("("+xpos+","+ypos+")",xpos,ypos);
                    if(xpos >450 && xpos < 850 && ypos >250 && ypos < 450){
                         g.drawString("("+xpos+","+ypos+")",xpos,ypos);
                    if((xpos==250&&ypos==50)  || (xpos== 650 && ypos==450 )){
                         g.drawString("("+xpos+","+ypos+")",xpos,ypos);
                    if(xpos >=50 && xpos <= 850 && ypos ==250 ){
                         g.drawString("("+xpos+","+ypos+")",xpos,ypos);
           /* public Dimension getPreferredSize()
                return size;
   

Answer 1

=)
For the boundaries of the globe you can test if the click was outside the globes by comparing the radius and the calculated distance from the center of each globe for each globe separately. The transform of the drawing the OP made is not a standard one so I'm having to comprehend the calculus of transformations I picked up last year and combine it with the linear algebra I learned this year ( might take until next week =( ). I tried implementing it by using weighted average procedures
i.e.
>
delta = ( 1 - t )*P + tQ>
where t is time in fraction of the total time and P and Q are two different points on a line. But there is also the effect of moving away from the equator for the longitude where the effect on the rate of change is increased when moving sideways ( longitude measures degrees around the earth from the prime meridian ) and when I tried to implement those two effects together, they seem to work for some parts but fail as I go diagonally (simply put) from 0deg,0deg which give false results in that the lat or lon (can remember which) is greater than the possible amount allowed ( i.e. abs_value > 180 for longitude or > 90 for latitude ).
Here's the code so far if you want to take a look at it:
I wasn't trying to worried too much about anything else but the algorithm for transforming the coords. I added the JLabel on the north side so I wouldn't have to look at the command prompt.
import java.awt.Dimension;
import javax.swing.JPanel;
import javax.swing.JFrame;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GradientPaint;
import java.awt.RenderingHints;
import java.awt.Point;
import java.awt.event.MouseListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.BorderLayout;
import javax.swing.JLabel;
public class DrawEarthPanel extends JPanel
     public static final long serialVersionUID = 1L;
     private static final Dimension size = new Dimension(900, 500); // width, height
     private static final GradientPaint backgradient = new GradientPaint(0, 0, Color.WHITE, 0, 350, Color.BLACK);
     private static final GradientPaint earthgradient = new GradientPaint(0, 50, Color.CYAN, 0, 450, Color.GREEN);
     private boolean mouseClicked;
     private int xpos = 0;
     private int ypos = 0;
     public DrawEarthPanel()
          addMouseListener( new MouseEvents() );
     public Dimension getPreferredSize()
          return DrawEarthPanel.size;
     public void paintComponent( Graphics g )
          super.paintComponent(g);
          Graphics2D g2 = (Graphics2D) g;
          g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
          g2.setPaint(backgradient);
          g2.fillRect(0, 0, 1000, 1000);
          g2.setPaint(earthgradient);
          g2.fillOval(50, 50, 400, 400);
          g2.fillOval(450, 50, 400, 400);
          g2.setColor(Color.BLUE);
          g.drawString("270",35,250);
          g.drawString("300",70,250);
          g.drawString("330",145,250);
          g.drawString("(0,0)",245,250);
          g.drawString("30",345,250);
          g.drawString("60",415,250);
          g.drawString("90",445,250);
          g.drawString("120",470,250);
          g.drawString("150",545,250);
          g.drawString("(180,0)",645,250);
          g.drawString("210",745,250);
          g.drawString("240",815,250);
          g.drawString("270",850,250);
          labelLatitudes( g, 255 );
          labelLatitudes( g, 650 );
          for ( int i=0; i<=180; i+=10 )
               int wLon = (int) (200 * Math.cos(Math.toRadians(i)));
               g2.drawOval(250-wLon, 50, 2*wLon, 400);
               g2.drawOval(650-wLon, 50, 2*wLon, 400);
               int wLat = (int) (200 * Math.sin(Math.toRadians(i)));
               g2.drawLine(250-wLat, 250-wLon, 250+wLat, 250-wLon);
               g2.drawLine(650-wLat, 250-wLon, 650+wLat, 250-wLon);
     private static final Point left_globe_origin = new Point( 250, 250 );
     private static final Point right_globe_origin = new Point( 650, 250 );
     private static final int globe_radius = 200;
     private void labelLatitudes(Graphics g, int x)
          g.drawString("90",x,48);
          g.drawString("60",x,77);
          g.drawString("30",x,150);
          g.drawString("-30",x,350);
          g.drawString("-60",x,425);
          g.drawString("-90",x,460);
     class MouseEvents extends MouseAdapter implements MouseListener
          public void mouseClicked( MouseEvent evt )
               xpos = evt.getX();
               ypos = evt.getY();
               System.err.println("DEBUG: xpos="+xpos+", ypos="+ypos);
               double lat = 0.0;
               double lon = 0.0;
               if ( xpos>50 && xpos<450 && distance(left_globe_origin,xpos,ypos) <= globe_radius ) // left globe
                    Point origin = left_globe_origin;
                    double radius = globe_radius;
                    double dx = xpos-origin.x;
                    double dy = -ypos+origin.y;
                    lat = (dy/(radius-dx))*90;
                    lon = (dx/(radius-dy))*90;
               //     lat = ypos - 250;
               //     lon = xpos - 250;
                    setLabel( String.format( "longitude >>> %.3f, latitude >> %.3f", lon, lat ) );
                    System.err.println( "DEBUG: lat=" + lat + ", lon=" + lon );
               else if ( xpos>450 && xpos<850 && distance( right_globe_origin,xpos,ypos) <= globe_radius ) // right globe
                    Point origin = right_globe_origin;
                    int radius = globe_radius;
                    int dx = xpos-origin.x;
                    int dy = ypos-origin.y;
                    lat = (1d*dx/radius+1d*dy/radius)*90;
                    lon = (1d*dx/radius+1d*dy/radius)*90;
               //     lat = ypos - 250;
               //     lon = xpos - 650;
                    setLabel( String.format( "longitude >>> %3.3f, latitude >> %3.3f", lon, lat ) );
                    System.err.println( "DEBUG: lat=" + lat + ", lon=" + lon );
               repaint();
     private static JLabel output = new JLabel( "Output of Longitude and Latitude" );
     public static void setLabel( String text )
          output.setText( text );
     public static double distance( Point origin, int x, int y )
          return Math.pow( Math.pow((x-origin.x),2)+Math.pow((y-origin.y),2), 0.5 );
     private static void createAndShowGUI()
          JFrame frame = new JFrame( "DrawEarthPanel" );
          frame.setLayout( new BorderLayout() );
          frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
          frame.setLocation(10, 10);
          frame.setContentPane(new DrawEarthPanel());
          frame.add( output, BorderLayout.NORTH );
          frame.pack();
          frame.setVisible(true);
     public static void main( String[] args )
          javax.swing.SwingUtilities.invokeLater(
               new Runnable()
                    public void run()
                         createAndShowGUI();
}The transform isn't a regular one since the OP kept his lat. lines straight so it's kind of weird to me right now.
Happy coding