ASCII to Binary and reverse in java
Just a few quick observations:


You mix business logic with UI code. Normally, you'd go for separation of concerns and move the conversion functions into a separate class which is used by the UI, but does not belong to the UI.
Running a separate thread: how long does the conversion take? 1 ms? 2? I really doubt that the overhead of thread-creation is necessary here. (Though it may indeed serve as an excercise!)
Binary to ascii validation: if the amount of bits does not match, you overwrite the user input? Thus, if I, the user, make a little mistake, type 319 bits instead of 320, you actually force me to start over? /me pissed user :-)


That's it for now (probably not complete.)