Reading and writing to file , getting null when i try to read file content

Question

i start by apologizing incase i have posted this question in the wrong forum
i am trying to iterate through a directory tree and pick all the subdirectories and put them in an arraylist . on the other hand , i am picking all the files and putting them in a different arraylist . After that i iterate through the arraylist , pick a folder , create a file in it search for all the files of the same type in its subfolders and write them to the newly created file
The problem i am running into is i i can't read the files and hence i can't write to the file .
My directory tree is in the format
c:\KPCData\\01\01\01\01\01\ file1_type1
c:\KPCData\\01\01\01\01\02\ file2_type1
where one one of the types is "covers" . i know this could be asking too much but i am at my tethers end , could someone please have a look at the code and tell me where i might be going wrong . you could zero in on the part where i have ************ before the a line of code thank you package directories;
import java.io.*;
import java.util.*;
public class Directories {
private static  ArrayList direcs= new ArrayList();
private static  ArrayList census= new ArrayList();
private static ArrayList vagrant= new ArrayList();
private static ArrayList hotel= new ArrayList();
private static ArrayList emigrant= new ArrayList();
private static ArrayList traveller= new ArrayList();
private static ArrayList longform= new ArrayList();
private static ArrayList cover= new ArrayList();
private static String parentPath = null;
private static File mycover = null;
private static File mytravel = null;
private static File myemigrant = null;
private static File mylong= null;
private static File myinstitution = null;
private static File myvagrant = null;
private static BufferedReader in;
private static BufferedWriter out;
private static String read,toread;
//function for listing the folder contents
class compareDirs implements Comparator
public int compare(Object one, Object two)
     int val=0;
     File file1 = (File)one;
     File file2= (File)two;
     String name1 = file1.toString();
     String name2= file2.toString();
     if (name1.length()==name2.length())
     val= name1.compareTo(name2);
     else
          if( name1.length()>name2.length())
               val=-1;
          if (name1.length()<name2.length())
               val=1;
     return val;
private  ArrayList recurs(File dir,File file) throws IOException
     File []files=dir.listFiles();
     for(int index=0;index<files.length ;index++)
          if(files[index].isDirectory())
               recurs(files[index],file);          
          }//if
          else
              census.add(files[index]);     
     }//for index
     return census;
} //recurs
//function for determining the number and paths of the folders
private ArrayList numDirs(File dirs)
     File []files=dirs.listFiles();
     for(int index=0;index<files.length ;index++)
          if(files[index].isDirectory())
               if (direcs.contains(files[index])==false)
               direcs.add(files[index]);
               numDirs(files[index]);     
          }//if
     }//for index
     return direcs;
public static void main(String[]args) throws IOException
          File myfile = new File("C:\\KPCData");
     File myfile2= new  File("C:\\KPCData\test.txt");
     Directories dir = new Directories();
     if (myfile.isDirectory())
     ArrayList myList=dir.recurs(myfile,myfile2);
     ArrayList mydir1 = dir.numDirs(myfile);
    ArrayList mydirs = new ArrayList();
    mydirs.add(mydir1.get(0));
     for (int x=0;x<mydir1.size();x++)
     {  int count=0;
          for (int y=0;y<mydirs.size();y++)
               if (x==y)
                    count++;
          if (count<1)
               mydirs.add(mydir1.get(x));
     Collections.sort( mydirs,dir.new compareDirs() );     
        for(int index1 =0 ;index1<mydirs.size();index1++)//print out directories
          File mydir=(File)mydirs.get(index1);
          File directory= (File)mydirs.get(index1);
          if(!mydir.getPath().contains("00"))//// if not leave node  create files for each file type
               String name1 =mydir.getPath();
               ArrayList ray=new ArrayList();
               String name="K";
             for (int index=0;index<name1.length();index++ )
                      if (name1.charAt(index)!='\\'&&name1.charAt(index)!='C'&&name1.charAt(index)!=':'&&name1.charAt(index)!='K'&&name1.charAt(index)!='P'&&name1.charAt(index)!='D'&&name1.charAt(index)!='a'&&name1.charAt(index)!='t')
                   name =name+(String.valueOf(name1.charAt(index)));
          // create a string
              name= name.substring(1);
               String trial = name+"_cover.dat";
               mycover = new File ( mydir,trial);
                 if (mycover.exists()) {
                      mycover.delete();
                      mycover.createNewFile();
                  } else {
                       mycover.createNewFile();
                 String addit = mydir.getParent().toString();
                mylong = new File (addit+"\\_long.dat");
                if (mylong .exists()) {
                      mylong.delete();
                      //mylong.createNewFile();
                  } else {
                        //mylong.createNewFile();
                          myemigrant = new File (mydir.getParent()+"\\_emigrant.dat");
                          if (myemigrant.exists()) {
                               myemigrant.delete();
                              // myemigrant.canWrite();
                            } else {
                                 //  myemigrant.canWrite();
               mytravel= new File (mydir.getParent().toString()+"\\_traveller.dat");
                if (mytravel.exists()) {
                    mytravel.delete();
                   // mytravel.createNewFile();
                  } else {
                       //mytravel.createNewFile();
                myinstitution = new File (mydir.getParent().toString()+"\\_institution.dat");
                if (myinstitution.exists()) {
                      myinstitution.delete() ;
                     // myinstitution.createNewFile();
                  } else {
                       //myinstitution.createNewFile();
                myvagrant = new File (mydir.getParent().toString()+"\\_vagrant.dat");
                if (myvagrant .exists()) {
                     myvagrant.delete();
                    // myvagrant.createNewFile();
                  } else {
                       //myvagrant.createNewFile();
     //}//initial
          for( int index2 =0;index2<myList.size();index2++)//loop the second one for individual files
               File file= (File)myList.get(index2);
               if (file.getParent().contains("00"))//leave node
                    parentPath =file.getParent().substring(0, file.getParent().length()-4);
               else
                    parentPath =file.getParent().substring(0, file.getParent().length()-3);
               if (parentPath.toString().compareTo(directory.getParent())==0&file.getName().contains("cover"))
                    try {
                         in = new BufferedReader(new FileReader(file));
                         out = new BufferedWriter( new  FileWriter(mycover));
                    ************     while ((read =in.readLine())!=null)
                         System.out.println("testing");//test whether i ever get in this section !!!
                         out.write(read);               
                         out.close();
                         in.close();
                    catch(NullPointerException e)
                         System.out.println(e);
                    catch(IOException e)
                         System.out.println("There was a problem:" + e);
}//class Directories

Answer 1

kingspalace wrote:
Dr Clap
The problem i am having is that whereas i am very sure that there are contents in the files i am trying to read , this part of the code Print the Values of parentPath,directory.getParent() and file.getName() here .In the start of this if condition to get a idea what stuff is coming here.
if (parentPath.toString().compareTo(directory.getParent())==0&file.getName().contains("cover"))
               {Are you trying to compare parentPath and directory.getParent() as Strings ? How about using equals() ?
Also are you aware that a single & and && are not one and the same ?
& will check nevertheless even if the string comparison on the parentPath returns true or false.
&& will not check file.getName() part if the String comparison part fails.
                    try {
                         in = new BufferedReader(new FileReader(file));
                         out = new BufferedWriter( new FileWriter(mycover));
                    ************     while ((read =in.readLine())!=null)
                         System.out.println("testing");//test whether i ever get in this section !!!
                         out.write(read);               
                         out.close();
                         in.close();
                    catch(NullPointerException e)
                         System.out.println(e);
                    catch(IOException e)
                         System.out.println("There was a problem:" + e);
                         }How about adding a simple Exception catch block here ,in case you miss anything ?
never gets executed executed (meaning ,according to the code, the files am reading have no content ). i am a bit new to files and directories in java . i am hence seeking advice on what i could be doing wrong .IN short,debugging your code will help you a lot.