Your task is to swap all letters A with O and all letters a with o in a RandomAccessFile. Simply read a byte at a time, and if you find a letter to be swapped, move one byte back.
For example, when you process a file containing the text of a well-known childrens song, it will be transformed into
Mory hod o little lomb, little lomb, little lomb, Mory hod o little lomb, its fleece wos white os snaw.