if (key[30] == "4848484919")
You said earlier that the bar code reader gives a sequence of bytes valued at 48 48 48 19 19. That seemed sensible and plausible.
But how can you possibly think that that is the same as a string with "4848484919"?
The first 4 characters would probably match a string "0001"
Then, to be even more illogical, you seem to think that all 10 characters of "4848484919" will fit into a single character in your array.
Perhaps I shouldn't have used the word "think".
...R