This is probably the best and most useful error message you will ever see. It tells you exactly what the problem is. You are using a cipher that requires padding so that the thing you are encrypting must have a length that is a multiple of 16 bytes.
You either have to pad your messages (e.g., with white space that you trim() after decryption), or you need to change to a non-padded cipher.
Thanks! By using few substrings coupled with some new commands, I fixed the problem. And you're right, this is probably the most self explanatory errors in java ;)