Create a JavaFX application that uses a TextField to get a message and encode or decode it using the classes described in Programming Project 5. Use buttons to control the kind of cipher used and to specify whether to encode or decode the message. Also use a TextField to get the number used in the constructor for the ciphers.

Programming Project 5.

Create an interface MessageDecoder that has a single abstract method decode(cipherText), where cipherText is the message to be decoded. The method will return the decoded message. Modify the classes SubstitutionCipher and ShuffleCipher, as described in Exercises 16 and 17, so that they implement MessageDecoder as well as the interface MessageEncoder that Exercise 15 describes. Finally, write a program that allows a user to encode and decode messages entered on the keyboard.

Exercise 15.

Create an interface MessageEncoder that has a single abstract method encode(plainText), where plainText is the message to be encoded. The method will return the encoded message.

Exercise 16.

Create a class SubstitutionCipher that implements the interface MessageEncoder, as described in the previous exercise. The constructor should have one parameter called shift. Define the method encode so that each letter is shifted by the value in shift. For example, if shift is 3, a will be replaced by d, b will be replaced by e, c will be replaced by f, and so on. (Hint: You may wish to define a private method that shifts a single character.)

Exercise 17.

Create a class ShuffleCipher that implements the interface MessageEncoder, as described in Exercise 15. The constructor should have one parameter called n. Define the method encode so that the message is shuffled n times. To perform one shuffle, split the message in half and then take characters from each half alternately. For example, if the message is abcdefghi, the halves are abcde and fghi. The shuffled message is afbgchdie. (Hint: You may wish to define a private method that performs one shuffle.)