Removing redundant letters then declaring string as charArr

Question

I'm trying to encrypt and decrypt strings using cipher text with a random keyword. The random keyword will be in a file "keyword.txt":

TROYONLINE

The string(s) will be in a separate file "input.txt":

THE QUICK BROWN FOX JUMPED OVER THE LAZY DOG
more lines here....

The cipher should use the keyword and a reversed alphabet without redundant letters. The cipher for keyword "TROYONLINE" would be:

TROYNLIEZXWVUSQPMKJHGFDCBA

Using this cipher, the above string will be encrypted to this:

HEN MGZOW RKQDS LQC XGUPNY QFNK HEN VTAB YQI

So far, I have this code:

import java.util.*;
import java.io.*;

public class reverseString
{
   public static void main(String [] args)
   {
      String abc = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
      String cipher = "";
      String newCipher;
      String encrypt = "";
      String ouput = "";

      BufferedReader readerKeyword = null;
      String key = "";
      try 
      {
          readerKeyword = new BufferedReader(new FileReader("keyword.txt"));          
      }
      catch (FileNotFoundException fnfex)
      {
         System.out.println(fnfex.getMessage() + " File not found.");
         System.exit(0); 
      }
      try
      {
         while ((key = readerKeyword.readLine()) !=null)
         {
           StringBuffer sb = new StringBuffer();

         int len = abc.length();

         for(int i = len -1;i>=0;i--)
              cipher = cipher + abc.charAt(i);

         newCipher = sb.append(key).append(cipher).toString();
         System.out.println(key);
         System.out.println(removeDuplicates(newCipher));

         }
      }
      catch (IOException ioex)
      {
         System.out.println(ioex.getMessage() + " Unable to read file.");
         System.exit(0);
      }

       BufferedReader readerInput = null;
        String lineInput;

       try 
       {
              readerInput = new BufferedReader(new FileReader ("input.txt"));           
       }
       catch (FileNotFoundException fnfex)
       {
         System.out.println(fnfex.getMessage() + " File not found.");
         System.exit(0); 
       }
       try
       {
          while ((lineInput = readerInput.readLine()) !=null)
          {
           char[] inputArray = lineInput.toCharArray();
           System.out.println(inputArray);
          }
       }
       catch (IOException ioex)
       {
         System.out.println(ioex.getMessage() + " Unable to read file.");
       }
   }

   static String removeDuplicates(String newCipher)
   {
      char[] charArr = newCipher.toCharArray();
      Set<Character> charSet = new LinkedHashSet<Character>();
      for(char ch : charArr)
      {
         charSet.add(ch);
      }
      StringBuffer StrBuf = new StringBuffer();
      for(char c : charSet)
      {
         StrBuf.append(c);

      }

      char[] cipherArray = removeDuplicates(newCipher).toCharArray();
      System.out.println(cipherArray);
      return StrBuf.toString();
   }
}

But I'm getting the below error:

TROYONLINE
Exception in thread "main" java.lang.StackOverflowError
    at java.util.HashMap.<init>(HashMap.java:456)
    at java.util.LinkedHashMap.<init>(LinkedHashMap.java:347)
    at java.util.HashSet.<init>(HashSet.java:161)
    at java.util.LinkedHashSet.<init>(LinkedHashSet.java:154)
    at reverseString.removeDuplicates(reverseString.java:83)
    at reverseString.removeDuplicates(reverseString.java:94)

With a ton of repeats of the last line ...(reverseString.java:94)

Answer 1

EDIT

Belows is how I would do this in your situation. But keep this in mind:

1. It makes no sense to have your key and the input text in files. If you have a lot of input lines then you would pass the key as a command line argument and have only one while loop that reads the input file and uses the same key to encrypt and decrypt. If you do have multiple keys, then you need to read each key and then read the whole input file line by line, then read the next key and read the input file again, etc., etc.
2. I have all of the logic in the main method but you should break it down into separate methods.

Main class:

String defaultAlphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

BufferedReader keyInputLine;
String key;
String cipher = "";
BufferedReader inputLine;
String inputText;
StringBuilder encryptedText;
StringBuilder decryptedText;

try {
    keyInputLine = new BufferedReader(new FileReader("keyword.txt"));
    
    while ((key = keyInputLine.readLine()) != null) {
        System.out.println("key: " + key);
        
        StringBuilder stringBuilder = new StringBuilder();
        
        // cipher is the key word plus the reverse of the alphabet
        cipher = stringBuilder.append(key).append(new StringBuilder(defaultAlphabet).reverse().toString()).toString();
        
        System.out.println("cipher: " + cipher);
        
        // remove duplicates from cipher
        cipher = removeDuplicates(cipher);
        
        System.out.println("replaced cipher: " + cipher);
    }
        
    inputLine = new BufferedReader(new FileReader("input.txt"));
    
    while ((inputText = inputLine.readLine()) != null) {
        System.out.println("original: " + inputText);
        
        encryptedText = new StringBuilder();
        
        for (char c : inputText.toCharArray()) {
            // find the input letter in the alphabet
            if (defaultAlphabet.indexOf(c) != -1) {
                // replace with same index from the cipher
                encryptedText.append(cipher.toCharArray()[defaultAlphabet.indexOf(c)]);
            } else {
                // if not found, use default (ex: space)
                encryptedText.append(c);
            }
        }
        
        System.out.println("encrypted: " + encryptedText.toString());
        
        decryptedText = new StringBuilder();
        
        for (char c : encryptedText.toString().toCharArray()) {
            // find the encrypted letter in the cipher
            if (cipher.indexOf(c) != -1) {
                // replace with same index from the cipher
                decryptedText.append(defaultAlphabet.toCharArray()[cipher.indexOf(c)]);
            } else {
                // if not found, use default (ex: space)
                decryptedText.append(c);
            }
        }
        
        System.out.println("decrypted: " + decryptedText.toString());
    }
} catch (IOException e) {
    e.printStackTrace();
}

The remove duplicates method:

static String removeDuplicates(String cipher) {
    Set<Character> charSet = new LinkedHashSet<Character>();
        
    for (char ch : cipher.toCharArray()) {
        charSet.add(ch);
    }
        
    StringBuilder stringBuilder = new StringBuilder();
        
    for (char c : charSet) {
        stringBuilder.append(c);
    }
        
    return stringBuilder.toString();
}

Previous Answer

It's like the error says, the "lineKeyword" variable is not initialized before being used. Consider that it is possible that there is an exception in your second try/catch. The exception is caught and you print a message but "lineKeyword" is still uninitialized.

There is a good answer here: Uninitialized variables and members in Java

The language defines it this way.

Instance variables of object type default to being initialized to null. Local variables of object type are not initialized by default and it's a compile time error to access an undefined variable.

See section 4.5.5 in here http://java.sun.com/docs/books/jls/second_edition/html/typesValues.doc.html#96595

Answer 2

I ended up putting my cipher code in a the while loop on the BufferedReader code and it cleared it up.

{
      BufferedReader readerKeyword = null;
      String key = "";
      try 
      {
          readerKeyword = new BufferedReader(new FileReader("keyword.txt"));          
      }
      catch (FileNotFoundException fnfex)
      {
         System.out.println(fnfex.getMessage() + " File not found.");
         System.exit(0); 
      }
      try
      {
         while ((key = readerKeyword.readLine()) !=null)
         {
         StringBuffer sb = new StringBuffer();

         int len = abc.length();

         for(int i = len -1;i>=0;i--)
              cipher = cipher + abc.charAt(i);

         newCipher = sb.append(key).append(cipher).toString();
         System.out.println(key);
         System.out.println(removeDuplicates(newCipher));

         }
      }
      catch (IOException ioex)
      {
         System.out.println(ioex.getMessage() + " Unable to read file.");
         System.exit(0);
      }