Enthuware

Just one more question.

If the handles are of RandomAccessFile, fileName2 will end up with 200 bytes because it writes from the beginning of the fileName2, overwriting the first 100 bytes and leaving the rest untouched. Is it correct?

yes, that is correct.

I am curious to what the question refers to. I don't understand the question. Is there an option to overwrite just parts of the existing file?

Not sure what you mean. The question contains a code that operates on two files. You are expected to know the outcome.
Yes, it is possible to modify just parts on an existing file.