Given the shifter string above, the plaintext "FAD" would be encrypted into "FGE" and the ciphertext "CGE" decrypts into the plaintext "BAD". Below are more in$-$depth descriptions of the required behavior:

public Substitution$()$

Constructs a new Substitution Cipher with an empty shifter.

public Substitution$($String shifter$)$

Constructs a new Substitution Cipher with the provided shifter.

Should throw an IllegalArgumentException if the length of the shifter doesn't match the number of characters within our Cipher's encodable range $($Cipher$.$TOTAL$\_$CHARS$),$ contains a duplicate character, or any individual character falls outside the encodable range $(<$ Cipher.MIN$\_$CHAR or $>$ Cipher.MAX$\_$CHAR$).$