Help changing my Centipede game objects from arrays to linked lists

I'm trying to recreate the old Atari Centipede game where the centipede snakes down the screen and the user shoots a bullet. There are also a bunch of other enemies such as the beetle flea and scorpion. I've got it working fairly well though I am not sure how to get my images to load faster or more seamlessly and I can't change all of my Objects from Arraylists, as they are in, and into LInked Lists.
I included my code and the outline he gave us to follow.Attachment 1240Attachment 1239