Chapter 8, Problem 8PP

Program Plan Intro

Encoder and Decoder using “JFrame”

Filename: “SubstitutionCipher.java”

• Define the “SubstitutionCipher” class which implements “MessageDecoder” and “MessageEncoder” interfaces.
  • Declare the “s” variable.
  • Define the constructor with the parameter “shift”.
    • Set the value to the declared variable.
  • Define the “encode” method.
    • Declare the string variable “msg” with the empty string.
    • The “for” loop iterate 0 to the length of the plain text.
      • Declare and assign the character to “c” variable.
      • Add the “msg” and “shift” value (by calling the “shift” method).
        • Return the “msg” value.
  • The “shift” method is used to move the value to the number of moves the user entered in the main class.
    • Declare the variable “ch” and assign the value.
    • Check the “c” value is in the series of “a” to “z”.
      • Shift the value after “c” value.
        • Check the “c” value is in the series of “A” to “Z”.
        • • Shift the value after “c” value.
        • Return the “msg” value.
  • Define the “decode” method.
    • Declare the string variable and assign empty string.
    • The “for” loop iterate 1 to length of cipher text.
      • Get the character index and stored it in the “ch” variable.
      • Append the characters.
        • Return the decoded string.

Filename: “ShuffleCipher.java”

• Define the class “ShuffleCipher” which implements “MessageDecoder” and “MessageEncoder” interfaces.
  • Declare the “n” integer variable.
  • Define the constructor along with a parameter “n”.
    • Set the value to the declared variable.
  • Define the “encode” method.
    • Declare and assign the value to the variable.
    • The “for” loop iterate till “n” numbers.
      • Call the “shuffle” method with an argument.
        • Return the encoded text.
  • Define the “shuffle” method.
    • Declare the “m” variable.
    • Find the midterm of the given plain text for splitting into two halves.
    • Declare the “a”, and “b” variables.
    • Call the “substring” with the arguments and stored it “a” variable.
    • Call the “substring” with the argument and stored it “b” variable.
    • The “for” loop is used to append the two substrings.
    • Finally return the string.
  • Define the “decode” method.
    • Declare the required variables.
    • The “for” loop shuffling “n” times to get the original plain text.
      • The inner “for” loop to get the even number of characters from encoded message.
      • Another inner “for” loop to get the odd number of characters from encoded message.
        • Assign the “t” to the “d” variable.
        • Set the “t” to empty.
        • • Return the decoded string.

Filename: “MessageEncoder.java”

• Define the “MessageEncoder” interface.
  • Declare the “encode” method along with the parameter “plainText”.

Filename: “MessageDecoder.java”

• Define the “MessageDecoder” interface.
  • Declare the “decode” method along with the parameter “cipherText”.

Filename: “CoderFrame.java”

• Create a main class “CoderFrame”.
  • Declare the constant variables.
  • Create the required variables for buttons, text fields, and label.
  • Define the constructor.
    • Set the window size.
    • Close the window after clicking “X” mark in the window.
    • Create four buttons.
    • Create the objects for the “ShuffleCipher” class.
    • Create the text fields, and label.
    • Set the layout.
    • Add the text fields, labels, and buttons on the output window.
  • Define “actionPerformed” method.
    • If the action command is equal to “Encode”, then execute “if” condition.
      • Get the text.
      • Set the text.
        • If the action command is equal to “Decode”, then execute “if” condition.
        • • Get the text.
          • Set the text.
        • If the action command is equal to “Shuffle Code”, then execute “if” condition.
        • • Get the text.
          • Declare the variable and covert the value as integer type.
          • Create the objects for the “ShuffleCipher” class.
        • If the action command is equal to “Substitution Code”, then execute “if” condition.
        • • Get the text.
          • Declare the variable and covert the value as integer type.
          • Create the objects for the “SubstitutionCipher” class.

Filename: “ShowCoder.java”

• Define the “ShowCoder” class.
  • Create an object for “CoderFrame” class.
  • Display the window.