Exception java

Bonjour,
mon code marche très bien sauf si la condition sur la derniere ligne du fichier source devient == true ; l'exception : Exception in thread "main" java.lang.NullPointerException
at allégerfile.maClass.main(maClass.java:35) est levé
svp aidez moi


voici mon code :

public static void main (String[] args) throws IOException {
                   // lecture fichier //
   BufferedReader in = new BufferedReader(new FileReader("D://pfe//copie.txt")); 
         out = new PrintWriter (new FileWriter ("D://mail.txt"));
   out2 = new PrintWriter (new FileWriter("d://Etrangé.txt"));
   out3 = new PrintWriter (new FileWriter("d://Editable.txt"));
         String line = in.readLine();
   
                               // défalcation //
                                     //compte mail //
  while (line != null){
   if ((line.startsWith("EXSTRS01")) && (line.substring(780,791).startsWith("EMAILVIDE")== false) && (line.substring(830,831).startsWith("O")))
    {  out.println(line); String s = in.readLine() ; 
      while (s.startsWith("EXSTRS01")==false )
      { out.println(s);
      s = in.readLine();}}
   else if ((line.startsWith("EXSTRS01"))&&(line.substring(696,746).startsWith("OEMAILVIDE")== false)&&(line.substring(746,747).startsWith("O")))
      {  out.println(line); String s = in.readLine() ; 
      while (s.startsWith("EXSTRS01")==false){ out.println(s);s = in.readLine();
      }
     
       }
     
   line = in.readLine();
    
   }
   in.close();
   out.close();