Assignment $4$ B: Caesar Cipher. One of the simplest methods to encrypt a message is to

$$shift$$ the letters by a literal value. For example, if we take the letter $$A$$ and shift it by $2,$ we get

$$C$.$ This $$substitution cipher$$ gets its name from the Roman emperor Julius Caesar, who was

one of the first person known to encode secret messages this way.

For this assignment, you will create a program that prompts the user for a message to encode,

as well as an offset to encrypt it with. You will then create and use the following methods:

$1.$ A validation method that takes in the message $($as a string$)$ and the offset integer

entered by the user. The method should return $$true$$ if the offset is between $0$ and $26$

inclusively and the message contains only letters and spaces. If it fails either criteria, it

should return $$false$.$

$2.$ If the validation method returns true, a second encryption method should be called. This

method also takes in the message $($as a string$)$ and the offset integer entered by the

user. It should convert the message to UPPERCASE, encrypt every letter in the

message, and leave the spaces as they were. It should then return the encrypted

message