Random monoalphabet cipher. The Caesar cipher, which shifts all letters by a fixed amount, is far too easy to crack. Here is a better idea. For the key, don't use numbers but words. Suppose the key word is FEATHER. Then first remove duplicate letters, yielding FEATHR, and append the other letters of the alphabet in reverse order. Now encrypt the letters as follows:

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Write a program that encrypts or decrypts a file using this cipher. The key word is specified with the -k command line option. The -d command line option specifies decryption. For example,

java Encryptor -d -k FEATHER encrypt.txt output.txt

decrypts a file using the keyword FEATHER. It is an error not to supply a keyword.

Complete the following files:

Encryptor.java

MonoalphabetCipher.java