This week's book giveaway is in the OCAJP forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide 1Z0-808 and have Jeanne Boyarsky & Scott Selikoff on-line! See this thread for details.
If you want to delete content from the end of a file, you do have a couple of faster options. You can use RandomAccessFile's setLength() method, or FileChannel's truncate() method, to change the file length to something smaller. This effectively deletes the bytes at the end. If you want to delete content from the beginning or middle, though - for that you really want to do as Stan suggested.