Ecryption program question

[joeF]

Hi:
I written an monoalphabet substitution encryption program. Can anyone point out mistakes or areas in which the code could be improved?
Thanks.

import java.io.FileReader;
import java.io.FileWriter;
import java.io.BufferedReader;
/**
A command line encryption program.
@version 1.0
*/
 public class Monoalphabet
{  
  public static void main(String args[])
 {
  int positionOfA = 'a';
  int positionzOfz = 'z';
  char [] cypher = null; 
  boolean decrypt = false;  
  FileWriter out = null;
  FileReader in = null;
  try
  {
   if (args.length < 3 || args.length > 5) usage();
   for (int i = 0; i < args.length; i++)
   {
    if (args[i].substring(0, 1).equals("-"))
    { String option = args[i].substring(1, 2);
       if (option.equals("d"))
        { String keyword = args[i + 1]; 
          if (keyword.length() <= 2)  missingKeyword(); 
          System.out.println(keyword.length());
          String keyTest = args[i + 1].substring(2, keyword.length());
          
           for (int j = 0; j < keyTest.length(); j++)
           {
            char test = keyTest.charAt(j);
            int k = (int) test;
            System.out.println(k);
    
            if (k < positionOfA || k > positionzOfz)
            {
              missingKeyword();                   
            }
            else
           { 
            String key = keyTest;
            cypher = makeCypher(removeDups(key));
            decrypt = true;
           }
         }
       }
        else if (option.equals("k"))
        {  
          String keyword = args[i]; 
          if (keyword.length() <= 2) missingKeyword();
          { String keyTest = args[i].substring(2, keyword.length());
           
           for (int j = 0; j < keyTest.length(); j++)
           {           
            char test = keyTest.charAt(j);
            int k = (int) test;
            System.out.println(k);
    
            if (k < positionOfA || k > positionzOfz)
            { missingKeyword();
            }
          }
         }
          String key = args[i].substring(2, keyword.length());
          cypher = makeCypher(removeDups(key));
        } 
     }
 
     else 
     {  if (in == null)
        { 
          in = new FileReader(args[i]);
        }
        else if (out == null)
        {   
         out = new FileWriter(args[i]);
        } 
     }
   }                 
 }
    catch (Exception e)
    { e.printStackTrace();
      System.out.println("Exception: " + e);
    }
    
    if (in == null || out == null) usage();
    
    try
    { if (decrypt)
      { decrypt(in, out, cypher);
        in.close();
        out.close();
      }
       
      else
      { encrypt(in, out, cypher);
        in.close();
        out.close(); 
      }  
    }
    
    catch (Exception e)
    {  System.out.println("Exception: " + e);
       System.exit(0);
       
    }   
  }
  
   /**
   Prints a message regarding a missing keyword.
   */
   public static void missingKeyword()
  {
    System.out.println("Missing Keyword");
    System.exit(1);
    
  }
  
   /**
   Prints a message describing proper usage and then exits.
   */
   public static void usage()
  {  System.out.println
       ("Usage: java Monoalphabet  [-d] [-kkeyword] infile outfile");
     System.exit(1);
  }
      
   /**
   A decryption method.
   
   @param   in     The input file.
   @param   out    The output file. 
   @param   cypher A character array.
  */
  public static void decrypt(FileReader in, FileWriter out, char [] cypher)
  {  int positionOfA = 'a';
     int alphabet = 26;
     
     char [] alpha = new char[alphabet];
     for (int i = 0; i < alpha.length; i++)
     {  alpha[i] = (char)(i + positionOfA);
        
     }
          
     BufferedReader infile  = new BufferedReader(in);
     try 
     {
     
     while (true)
     {
         { int next = in.read();
           if (next == -1) return;
           char whatever = (char) next;           
          
          if (Character.isLetter(whatever))
          {  for (int i = 0; i < cypher.length; i++)
            {  if (cypher[i] == whatever)
                         
              {
                int position = i;
                char ch = alpha[i];
                out.write(ch);               
               }
             }
           
           }
           else
          {
           char ch = whatever;
           out.write(ch);
          } 
        }
       }
      
     }
   
    catch (Exception e) 
    {
      System.out.println("Exception: " + e);
    }
     
     
  }
   /**
   An encryption method.
   
   @param   in     The input file.
   @param   out    The output file. 
   @param   cypher A character array.
   */
  
   public static void encrypt(FileReader in, FileWriter out, char[] cypher)
  {  int positionOfA = 'a';
     BufferedReader infile  = new BufferedReader(in);
     try
     {
     while (true)
     {
        { int next = in.read();
          if (next == -1) return;
          char whatever = Character.toLowerCase((char)next);
          if (Character.isLetter(whatever))
          {
           char ch = cypher[(int)whatever -  positionOfA];
           out.write(ch); 
          }  
          else
          {
           char ch = whatever;
           out.write(ch); 
          } 
       }
     }
 }
    catch (Exception e) 
    {
      System.out.println("Exception: " + e);
    }
  }
 
  /**
  A method for removing duplicate letters from a string.
 
  @param   key   A keyword used for encryption. 
  @return  keep  A string with a keyword plus reverse alphabet
                 with duplicate letters removed. 
  */
  public static String removeDups(String key)
  { 
    String keep = "";
    key = key + "zyxwvutsrqponmlkjihgfedcba";
    System.out.println("The key is " + key);   
    for (int i = key.length() - 1; i > -1 ; i--)
   
    if (i == key.indexOf(key.charAt(i)))
    {
     keep = key.charAt(i) + keep;
    
    }
      
    return keep;  
     
  }
  /**
  A method for copying a string to a character array.
  
  @param   keep       A string containing a keyword and reverse alphabet.
  @return  keepArray  Character array containing a keyword plus 
                      reverse alphabet.
 */
  public static  char[] makeCypher(String keep)
  {
      char  keepArray [];
      keepArray = keep.toCharArray();
      return keepArray;
  }
      
}

(edited by Cindy to change backslash to slash so that code tags would work)
[ December 16, 2002: Message edited by: Cindy Glass ]
[ December 16, 2002: Message edited by: joeF ]

[Cindy Glass]

Handy man,
Welcome to JavaRanch,
we hope you’ll enjoy visiting as a regular however, your name is not in keeping with our naming policy
here at the ranch. Please change your display name to an appropriate name as shown in the policy.
You can change your profile here.
Thanks again and we hope to see you around the ranch!!
Cindy

[joeF]

Hi:
I changed my name in the profile.
Regards,
Joe

[Cindy Glass]

joeF,
I think that you missed the part about how it should be 2 separate names with more than one letter.
Why don't you try again .