Thread: Null pointer exception

Hey folks,
So I've been working a little program that draws maps. It reads in a CSV file with city names, coordinates, distances, and interconnecting highways. Its supposed to draw red lines (highways) between black dots (cities). However, I keep getting a null pointer exception, and I can't figure it out! here's my code so far, and I'll attach the CSV.

here's the main program:

package Maps2;
 
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.MouseEvent;
import java.io.File;
import javax.swing.JFileChooser;
import javax.swing.JPanel;
 
/**
 *
 * @author stu696084
 */
public class Map extends javax.swing.JFrame {
 
  JFileChooser fileChooser = new JFileChooser();
  public City start;
  public City end;
    /** Creates new form Map */
    public Map() {
        initComponents();}
        public class MyPanel extends JPanel {
  @Override
        @SuppressWarnings("static-access")
       public void paint(Graphics g) {
           super.paint(g);
           for(City c: City.cities) {
                 Color z= Color.BLACK;
 
               if (c == start){
                   z = Color.RED;
 
 
               }
               else if (c == end) {
                     z = Color.BLUE;
               }
                 g.setColor(z);
                 g.fillOval((int)start.p.px, (int)start.p.py, 15, 15);
                 g.setColor(Color.RED);
                 g.drawLine((int)start.p.px, (int)start.p.py, (int)end.p.px, (int)end.p.py);
           }
 
           // Place code to draw the map here
           }
       }
 
 
 
    /** This method is called from within the constructor to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
     */
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {
 
        theMap = new MyPanel();
        loadMap = new javax.swing.JButton();
        showMap = new javax.swing.JButton();
        showDirections = new javax.swing.JButton();
        jLabel1 = new javax.swing.JLabel();
 
        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
 
        theMap.setBackground(new java.awt.Color(102, 204, 0));
        theMap.setPreferredSize(new java.awt.Dimension(1000, 650));
        theMap.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseClicked(java.awt.event.MouseEvent evt) {
                theMapMouseClicked(evt);
            }
        });
 
        org.jdesktop.layout.GroupLayout theMapLayout = new org.jdesktop.layout.GroupLayout(theMap);
        theMap.setLayout(theMapLayout);
        theMapLayout.setHorizontalGroup(
            theMapLayout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(0, 1000, Short.MAX_VALUE)
        );
        theMapLayout.setVerticalGroup(
            theMapLayout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(0, 650, Short.MAX_VALUE)
        );
 
        loadMap.setText("Load Map");
        loadMap.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                loadMapActionPerformed(evt);
            }
        });
 
        showMap.setText("Show Map");
        showMap.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                showMapActionPerformed(evt);
            }
        });
 
        showDirections.setText("Show Directions");
        showDirections.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                showDirectionsActionPerformed(evt);
            }
        });
 
        jLabel1.setText("jLabel1");
 
        org.jdesktop.layout.GroupLayout layout = new org.jdesktop.layout.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(layout.createSequentialGroup()
                .add(layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
                    .add(layout.createSequentialGroup()
                        .add(50, 50, 50)
                        .add(theMap, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                        .add(52, 52, 52)
                        .add(layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
                            .add(showMap)
                            .add(loadMap)
                            .add(showDirections)))
                    .add(layout.createSequentialGroup()
                        .add(464, 464, 464)
                        .add(jLabel1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 310, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)))
                .addContainerGap(80, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
            .add(layout.createSequentialGroup()
                .add(6, 6, 6)
                .add(jLabel1, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 23, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
                .addPreferredGap(org.jdesktop.layout.LayoutStyle.UNRELATED)
                .add(layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
                    .add(layout.createSequentialGroup()
                        .add(loadMap)
                        .add(34, 34, 34)
                        .add(showMap)
                        .add(29, 29, 29)
                        .add(showDirections))
                    .add(theMap, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE))
                .addContainerGap(41, Short.MAX_VALUE))
        );
 
        pack();
    }// </editor-fold>                        
 
    private void loadMapActionPerformed(java.awt.event.ActionEvent evt) {                                        
      int retval = fileChooser.showOpenDialog(this);
      if (retval == JFileChooser.APPROVE_OPTION) {
            File file = fileChooser.getSelectedFile();
        Input.readFile(file);
      }
        // TODO add your handling code here:
    }                                       
 
    private void showMapActionPerformed(java.awt.event.ActionEvent evt) {                                        
 
 
            for (City c : City.cities) {
                System.out.println(c.name + " Is at " + c.p.px + ", " + c.p.py);
 
 
                for (Road r : c.roads) {
                    System.out.println("  Road " + r.name + " Goes to " + r.endCity.name + " (" + r.length + ", " + r.time + ")");
 
                }
 
 
        }  // TODO add your handling code here:
        // TODO add your handling code here:
    }                                       
 
    private void showDirectionsActionPerformed(java.awt.event.ActionEvent evt) {                                               
        // TODO add your handling code here:
    }                                              
 
    private void theMapMouseClicked(java.awt.event.MouseEvent evt) {                                    
       for(City c : City.cities) {
 
           if(Point.close(evt.getX(), evt.getY())==true) {
               c = start;
           }
           else if (c==start) {
               c = end;
           }
       }
        // TODO add your handling code here:
    }                                   
 
    /**
    * @param args the command line arguments
    */
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new Map().setVisible(true);
            }
        });
    }
 
    // Variables declaration - do not modify                     
    private javax.swing.JLabel jLabel1;
    private javax.swing.JButton loadMap;
    private javax.swing.JButton showDirections;
    private javax.swing.JButton showMap;
    private javax.swing.JPanel theMap;
    // End of variables declaration                   
 
}

Here's the City and Road classes

package Maps2;
 
import java.util.ArrayList;
 
/**
 *
 * @author stu696084
 */
public class City {
 
    public Point p;
    public String name;
    public static ArrayList<City> cities = new ArrayList<City>();
    public ArrayList<Road> roads = new ArrayList<Road>();
 
    public City(String name, int x, int y) {
        this.name = name;
        this.p = new Point(x, y);
 
        cities.add(this);
 
    }
 
    public boolean isCity(String s) {
        return s.equals(name);
    }
 
    public static City findCity(String s) {
        for (City c : cities) {
            if (c.isCity(s)) {
                return c;
            }
        }
        return null;
    }
 
    public static void Clear() {
        City.cities.clear();
    }
}

package Maps2;
 
/**
 *
 * @author stu696084
 */
public class Road {
 
    public City startCity, endCity;
    public int length, time;
    public String name;
 
    public Road(String name, City startCity, City endCity, int length, int time) {
        this.startCity = startCity;
        this.endCity = endCity;
        this.length = length;
        this.time = time;
        this.name = name;
    }
 
    @Override
    public String toString() {
        return (startCity + "and" + endCity);
    }
}

and finally the Input and Point classes:

package Maps2;
 
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
 
/**
 *
 * @author stu696084
 */
public class Input {
 
    public static void readFile(File file) {
        City.Clear();
 
        try {
            BufferedReader reader = new BufferedReader(new FileReader(file));
            String s;
            Boolean road = false;
            while ((s = reader.readLine()) != null) {
                String[] strings = s.split(",");
                if (strings.length == 0) {
                    System.out.println("nothin");
                    road = true;
                } else if (road == false) {
                    City c = new City(strings[0], Integer.parseInt(strings[1]), Integer.parseInt(strings[2]));
 
 
 
                } else {
                    Road r = new Road(strings[0], City.findCity(strings[1]), City.findCity(strings[2]), Integer.parseInt(strings[3]), Integer.parseInt(strings[4]));
                    Road r2 = new Road(strings[0], City.findCity(strings[2]), City.findCity(strings[1]), Integer.parseInt(strings[3]), Integer.parseInt(strings[4]));
                    r.startCity.roads.add(r);
                    r2.startCity.roads.add(r2);
                }
 
            }
        } catch (Exception e) {
            System.out.println("File Error");
        }
    }
 
}

package Maps2;
 
/**
 *
 * @author stu696084
 */
public class Point {
 
    static double px, py;
double x, y;
    @SuppressWarnings("static-access")
    public Point(double x, double y) {
        this.x = x;
        this.y = y;
        this.px = x * 2;
        this.py = y * 1.3 - 30;
    }
 
    public static boolean close(double mousex, double mousey) {
        return (mousex - px) * mousex - px + (mousey - py) * (mousey - py) < 25;
 
    }
 
    @Override
    public String toString() {
        return "(" + x + "," + y + ")";
    }
}

And I think the CSV is attached, but let me know if it doesn't work for you.
Any help on this would be great guys, thanks a lot!

Where are you exactly getting the Null pointer exception, it's too difficult to trace the whole program for me as i have not much time. Thanks for if you will be able to tell that in what area, this exception is being occured???