Chapter 21, Problem 3PP

Program Plan Intro

Vigenere cipher

Program plan:

• In the file “VigenereCipher.java”, import necessary packages and create a class “VigenereCipher”,
  • Declare string variable.
  • Define the constructor to initialize the variables.
  • Define the method “processStream()” to process the contents of a stream.
  • Define the method “process()” to process a single byte for encryption or decryption.
• In the file “Encryptor.java”, import necessary packages and create a class “Encryptor”,
  • Define the method “main()”,
    • Initialize the necessary variables.
    • Execute “try” statement,
      • Initialize the variable.
      • Execute “while” loop till the length of the argument,
        • If the argument id “-d”,
        • • Set the Boolean value to true.
        • Otherwise check if the argument is “-k”,
        • • Increment the value by 1.
          • Check the condition,
            • If it is true, set the key.
        • Otherwise, if the input file is null,
        • • Get the input file.
        • Otherwise, if the output file is null,
        • • Get the output file.
      • If either the input or output or key is null,
        • Print the string.
      • Otherwise,
        • Create the input stream.
        • Create the output stream.
        • Create an object for “VigenereCipher”.
        • Call the method “processStream()”.
        • Close the input and output file.
    • Catch if exception occur,
      • Handle the exception.