Coding message

Hi, i'm new to arduino coding.
I have a question.

I use a lcd 16x2, to show my message send with bt from my android app.

How can i do, to show all letter from message one time, no metter how many times that letter it is repetead.

Sorry for my bad english

Keep a list of hashes for the previous N messages (letters). If a new message has the same hash as a previous message discard the new message.