P White

Guys,

Thanks for all your help.

I have taken all advice on board and changed the variables to lower case.

I took a break from this and went to the pub last night where I had a thought. What if I put in an extra step?
My thoughts were that I was not sure how the underlying Java system was handling adding the extra linefeeds then shuffling during one operation. Were the extra line feeds a problem?

So I changed the code to:

[ BufferedReader reader = new BufferedReader(new FileReader("Files/temp.dat")); String nextLine = reader.readLine(); while (nextLine != null) { // nextLine = nextLine.replace("~", "\n"); data.add(nextLine); nextLine = reader.readLine(); } reader.close();//just a good idea apparently String alterText = null; int i; for (i = 0; i < (data.size()-1); i++) alterText = data.get(i); alterText = alterText.replace("~", "\n"); data.set(i, alterText); Collections.shuffle(data); return data; }] [code=java]

I initially got an error reading the array as ot counted to 130 and then errored so I put a -1 on the count to stop this. My file has only 128 lines.
This seems to have cured the problem.

I thought you might like to know the solution.

Paul,

Thank you your comments make sense.

I will in future use lower case names for variables.

Paul,

Thank you for your patience.
I have moved the code as you suggest to make it readable I hadn't realised you needed to put it inside the bracket.

Looking at my code I see your point. I am new to this and have trouble passing vaiables between classes (sometimes it seems to work and sometimes it doesn't) hense you will find hard coded bits referring to variables in an another class. This is what happened here the fliename was not passed so I hard coded it as a work around.

I am trying to learn java by creating working apps this is my third.

The code is not pretty I know but until I have spent more time writing bits and peices I will never get to the bottom of my errors and find the solutions to them.

And of course a thank you to everyone else who has taken the time to try to help.

This is the entire code from my csv file reader

I have been experimenting and there are some reduntant lines of code i.e. boolean ready = false:
FYI I was trying to use wait() to allow the shuffle to complete but this concept is completely beyond me................

If I enable the index counter just above I get a seemingly random count and then the error at ColQ.add(temp.get(0));
This is always the line indicated.

Please bear in mind I only get an error when I enable the line "Collections.shuffle(data);

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
at java.util.ArrayList.rangeCheck(Unknown Source)
at java.util.ArrayList.get(Unknown Source)
at quiz.ReadEncryptedFile.ReadCSVFile(ReadEncryptedFile.java:115)
at quiz.UserInterface.main(UserInterface.java:194)

Line 3 should only allow the file to be read if it exists and can be read - this bit (I think) is not causing me a problem, even if it not the way to check.
I have disabled it anyway and tried agian but am still getting the same error.

Thank you all very much.

[/package quiz; import java.io.BufferedReader; import java.io.File; import java.io.FileNotFoundException; import java.io.FileReader; import java.io.IOException; import java.util.ArrayList; import java.util.Collections; public class ReadEncryptedFile{ static ArrayList<String> data = new ArrayList<String>(); public static final ArrayList<String> ColQ = new ArrayList<String>(); public static final ArrayList<String> ColA1 = new ArrayList<String>(); public static final ArrayList<String> ColA2 = new ArrayList<String>(); public static final ArrayList<String> ColA3 = new ArrayList<String>(); public static final ArrayList<String> ColA4 = new ArrayList<String>(); public static final ArrayList<String> ColCorrect = new ArrayList<String>(); public static final ArrayList<String> ColPicture = new ArrayList<String>(); public static final ArrayList<String> ColExplanation = new ArrayList<String>(); public static final ArrayList<String> ColURL = new ArrayList<String>(); // String filename; boolean ready = false; public ArrayList<String> readAsStrings(File filename) throws FileNotFoundException, IOException { String Filename = "" + UserInterface.filename; new TestDecryptor(); TestDecryptor.FileToDecrypt(Filename); /**returns all of the data in a file as Strings given the File object*/ int index = 0; BufferedReader reader = new BufferedReader(new FileReader("Files/temp.dat")); String nextLine = reader.readLine(); // if (filename.exists() && filename.canRead()){ while (nextLine != null) { nextLine = nextLine.replace("~", "\n"); data.add(nextLine); nextLine = reader.readLine(); // System.out.print(index + " "); // System.out.println(nextLine); // index = index + 1; } reader.close();//just a good idea apparently Collections.shuffle(data); return data; } // Collections.shuffle(data); // return data; // } public ArrayList<String> extractFromCommas(String dataLine) { //Gives back the data that is found between commas in a String ArrayList<String> data = new ArrayList<String>(); String theString = ""; for (int i = 0; i < dataLine.length(); i++) {//go down the whole string if (dataLine.charAt(i) == ',') { if (i == 0) { //do nothing } else { data.add(theString);//this means that the next comma has been reached theString = "";//reset theString Variable } } else { theString = theString + dataLine.charAt(i);//otherwise, just keep piling the chars onto the cumulative string // System.out.println(theString); } } if (!theString.equalsIgnoreCase(""))//only if the last position is not occupied with nothing then add the end on { data.add(theString); } return data; } /* public ArrayList findString(ArrayList data, String searchString) { //Finds a string in an arraylist of strings ArrayList foundStrings = new ArrayList(); for (int i = 0; i < data.size(); i++) { if (data.get(i).toString().contains(searchString)) { foundStrings.add(data.get(i).toString()); } } return foundStrings;//returns null if the string is not found. } */ public static ArrayList<String> ReadCSVFile (String filename){ ReadEncryptedFile File = new ReadEncryptedFile(); ArrayList<String> AL_A = new ArrayList<String>(); int i; try { AL_A = File.readAsStrings(new File("Files/temp.dat")); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } for(i=0;i<(AL_A.size()-1);i++){ // System.out.println("Index = " + i); ArrayList<String> temp = new ArrayList<String>(); temp = File.extractFromCommas(AL_A.get(i).toString()); ColQ.add(temp.get(0)); ColA1.add(temp.get(1)); ColA2.add(temp.get(2)); ColA3.add(temp.get(3)); ColA4.add(temp.get(4)); ColCorrect.add(temp.get(5)); ColPicture.add(temp.get(6)); ColExplanation.add(temp.get(7)); ColURL.add(temp.get(8)); File Filename = (new File("Files/temp.dat")); Filename.delete(); } return ColQ; } } ] [code=java]

Matthew,

Thank you for the time you have taken to look at this for me.

If I add a a counter and a line to printout the information contained in "data" like this there are 128 lines of data.

Also if I add a line to print "data" following reader.close() I can see all the data up to and including the last line from my file.

int index = 0; BufferedReader reader = new BufferedReader(new FileReader("Files/temp.dat")); String nextLine = reader.readLine(); if (filename.exists() && filename.canRead()){ while (nextLine != null) { nextLine = nextLine.replace("~", "\n"); data.add(nextLine); nextLine = reader.readLine(); System.out.print(index + " "); System.out.println(nextLine); index = index + 1; } reader.close();//just a good idea apparently } // Collections.shuffle(data); return data; }

John,

Thank you for this information. It will come in very useful for next time.

I very much appreciate your time in helping me.

Thank you

Paul

Hi,

I have almost finished a program to create and take quizes.

The quiz creator is finished but I have problem with the quiz taker.

The quiz file is a basic .csv file

To stop the student from reading the .csv file I am encrypting the file.

1. I am reading the csv file replacing \r\n with a a ¬, replacing \n with ~, and then replacing the ¬ with \r\n
2. I am then encrypting the file.

When the quiz runs I am decypting the file, replacing the ~ with \n and returning the data to csv format.

The questions and answers display correctly but I want to shuffle the questions

As soon as I add the collections.shuffle into the code I get this error

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
at java.util.ArrayList.rangeCheck(Unknown Source)
at java.util.ArrayList.get(Unknown Source)
at quiz.ReadEncryptedFile.ReadCSVFile(ReadEncryptedFile.java:110)
at quiz.UserInterface.main(UserInterface.java:194)

I think this is caused because the collections.shuffle has not completed.
I have tried to make the program pause but this just delays the error from appearing.

My csv file reader contains this code which is where the problem lies.

BufferedReader reader = new BufferedReader(new FileReader("Files/temp.dat")); String nextLine = reader.readLine(); if (filename.exists() && filename.canRead()){ while (nextLine != null) { nextLine = nextLine.replace("~", "\n"); data.add(nextLine); nextLine = reader.readLine(); } reader.close();//just a good idea apparently } Collections.shuffle(data); return data;

I have found a work around to this now.

I am reading the quiz file and replacing the \r\n with a seldom used character and the \n with another seldom used character saving this file to disk then encrypting.

after decryption I am replacing the characters with \r\n and \n respectively.

Perhaps not the best solution but it is working.

and this is the decryptor so that you get your csv file back.

import java.io.*; import java.security.*; import java.security.spec.InvalidKeySpecException; import javax.crypto.*; import javax.crypto.spec.*; public class TestDecryptor { private static String password; private static FileInputStream inFile; private static FileOutputStream outFile; public static String FileToDecrypt(String filename) { { // File to decrypt. filename = "temp.enc"; // System.out.println("FileDecryptor " + filename); password = "12345678"; try { inFile = new FileInputStream(filename); outFile = new FileOutputStream("temp.csv"); PBEKeySpec keySpec = new PBEKeySpec(password.toCharArray()); SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBEWithMD5AndDES"); SecretKey passwordKey = keyFactory.generateSecret(keySpec); // Read in the previouly stored salt and set the iteration count. byte[] salt = new byte[8]; inFile.read(salt); int iterations = 100; PBEParameterSpec parameterSpec = new PBEParameterSpec(salt, iterations); // Create the cipher and initialize it for decryption. Cipher cipher = Cipher.getInstance("PBEWithMD5AndDES"); cipher.init(Cipher.DECRYPT_MODE, passwordKey, parameterSpec); byte[] input = new byte[64]; int bytesRead; while ((bytesRead = inFile.read(input)) != -1) { byte[] output = cipher.update(input, 0, bytesRead); if (output != null) outFile.write(output); } byte[] output = cipher.doFinal(); if (output != null) outFile.write(output); inFile.close(); outFile.flush(); outFile.close(); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } catch (IllegalBlockSizeException e) { e.printStackTrace(); } catch (BadPaddingException e) { e.printStackTrace(); } catch (InvalidKeyException e) { e.printStackTrace(); } catch (InvalidAlgorithmParameterException e) { e.printStackTrace(); } catch (InvalidKeySpecException e) { e.printStackTrace(); } catch (NoSuchAlgorithmException e) { e.printStackTrace(); } catch (NoSuchPaddingException e) { e.printStackTrace(); } return null; } } }

Hi,

Can someone please point me in the right direction. I have been at this all day and am no closer to a solution than I was first thing this morning.

I have written a simple quiz program that reads its information form a csv file. I would like to encrpt the data as the csv file indicates which asnwer is correct.

When I encrypt and decrypt the csv file I am losing any line feeds in the file which messes up the formating of the text in my text areas.

I don't know why perhaps someone would point me in the right direction.

File encryptor:

import java.io.*; import javax.crypto.*; import javax.crypto.spec.*; import java.security.InvalidAlgorithmParameterException; import java.security.InvalidKeyException; import java.security.NoSuchAlgorithmException; import java.security.spec.InvalidKeySpecException; import java.util.*; public class FileEncryptor { private static String filename; private static FileInputStream inFile; private static FileOutputStream outFile; static String result; public FileEncryptor(File file) throws NoSuchAlgorithmException, InvalidKeySpecException, NoSuchPaddingException, IOException, IllegalBlockSizeException, BadPaddingException, InvalidKeyException, InvalidAlgorithmParameterException { // File to encrypt. filename = "temp.csv"; // Password must be at least 8 characters (bytes) long String password = "12345678"; inFile = new FileInputStream(filename); outFile = new FileOutputStream("temp.enc"); // Use PBEKeySpec to create a key based on a password. // The password is passed as a character array PBEKeySpec keySpec = new PBEKeySpec(password.toCharArray()); SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBEWithMD5AndDES"); SecretKey passwordKey = keyFactory.generateSecret(keySpec); // PBE = hashing + symmetric encryption. A 64 bit random // number (the salt) is added to the password and hashed // using a Message Digest Algorithm (MD5 in this example.). // The number of times the password is hashed is determined // by the interation count. Adding a random number and // hashing multiple times enlarges the key space. byte[] salt = new byte[8]; Random rnd = new Random(); rnd.nextBytes(salt); int iterations = 100; //Create the parameter spec for this salt and interation count PBEParameterSpec parameterSpec = new PBEParameterSpec(salt, iterations); // Create the cipher and initialize it for encryption. Cipher cipher = Cipher.getInstance("PBEWithMD5AndDES"); cipher.init(Cipher.ENCRYPT_MODE, passwordKey, parameterSpec); // Need to write the salt to the (encrypted) file. The // salt is needed when reconstructing the key for decryption. outFile.write(salt); // Read the file and encrypt its bytes. byte[] input = new byte[64]; int bytesRead; while ((bytesRead = inFile.read(input)) != -1) { byte[] output = cipher.update(input, 0, bytesRead); if (output != null) outFile.write(output); } byte[] output = cipher.doFinal(); if (output != null) outFile.write(output); inFile.close(); outFile.flush(); outFile.close(); result = "File " + filename + " Encrypted"; } }