I dont really need to post the code because im going to start again.
I did try and change the plaintext character to its ascii number + 3 and then convert it back however i can only use charcters in the range of 33-126 (
http://www.cs.utk.edu/~pham/ascii_table.jpg) I understand
So for example i have
text: Hello123~
ascii: H=72, e=101, l=108, l=108, o=111, 1=49, 2=50, 3=51, ~=176
if i was to for example add 1 to each ascii number the ~ will be come 177 which when converted back to its charcter will be the DEL caharcter. So i need some wat to wrap it around so if it goes over 176 it goes back to 33 and up .
Also i have had problems when i convert the test to a Char array the spaces become '#' characters