Write a program that can perform the Caesar cipher for English messages that include both upper- and lowercase characters. Implement a class, SubstitutionCipher, with a constructor that takes a string...

that include both upper- and lowercase characters.

Implement a class, SubstitutionCipher, with a constructor that takes a

string with the 26 uppercase letters in an arbitrary order and uses that for

the forward mapping for encryption (akin to the self. forward string in

our CaesarCipher class of Code Fragment 5.11). You should derive the

backward mapping from the forward version.