Java code.

I have this programming problem that already has been solved:

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.

Create a class SubstitutionCipher that implements the interface MessageEncoder, as described above. The constructor should have one parameter called shift. Define the method encode so that each letter is shifted by the value in shift. Defne 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.)

Create a class ShuffleCipher that implements the interface MessageEncoder, as described above. 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.

What I actually need is to modify the given code from already solved programming problem 2

the code is given in this link https://www.chegg.com/homework-help/questions-and-answers/messageencoder-java-create-interface-messageencoder-single-abstract-method-encode-plaintex-q5674325

I need the following modifications:

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 Programming Problem 2, above, so that they implement MessageDecoder as well as the interface MessageEncoder described above. Finally, write a program that allows a user to encode and decode messages entered on the keyboard.