To clarify, I know why my game is running slow. I have a lot of different objects in the current area and it has to tick and render all of those objects. I just don't know how to fix the problem without just making less objects.

The answer I am looking for is more of a concept of how I can go about fixing this problem rather than just making a bunch of code for me to paste into my game.

I am designing my games based off of tutorials by RealTutsGML. There where some issues I had to work around with his method of building games, but I figured them out.

So every tick in my game, I have to look through all of the objects that currently exist. The more objects that exist, the longer it takes to process all of them. I need to find a way to help free up memory if those objects are currently not in view, for example. I know games like Minecraft use chunks to free up unused memory. (Blocks outside of the view distance are not generated) What can I do to allow for an environment with many objects without causing so much lag? I want to be able to have a big level without having so much lag from all the objects that have to be ticked and rendered.

Another thing that I will clarify is that all of the objects loaded into the levels are held in a LinkedList so that I can easily create and destroy objects. Every tick, I run a for loop through those linked lists to process every objects behavior and how they are rendered.

[EDIT APRIL 28]

The objects in the game I was working on are organized in a very grid-like format. So that includes the tiles, the player, and all of the other game objects.

You haven't given too much information about your game (I'm not going to look through the tutorial either). You may want to give more background information, and maybe some code snippets.

I know one thing about your code with certainty: you are using linked lists. Linked lists, especially when you add and remove things from the middle, are slow. The reason for this is memory (or cache) locality. When they say computers are growing exponentially faster, they meant the processor is. Your data needs to be transported from its home in memory to another location to a place where it can be used. When data is needed, it is transported by a bus, which also brings neighboring data. (Note that "bus" is actually the technical name for the component.) Linked lists, especially how you're using them, manipulate data in a way that destroys neighborhoods of data. As a result, the bus essentially becomes a "taxi", getting data one at a time. And the bus, according to the graph, is a stunning 10x faster than the computers of the 1980's (remember, the graph has an exponential scale).

Also, it seems to me like you probably don't need to tick EVERY object EVERY frame. Yes some objects, like mobs, will need to tick every frame (if they are close enough to be active). From what I assume your game looks like, you have each block of grass being its own object and ticking every frame. Stop watching the grass grow.

MineCraft, for example, will only tick sand blocks when a neighboring block changes (which is why sand generated in the air will only fall when disturbed).

You may want to check these pages out:

Question about memory locality.

Question about linked lists and memory locality

Site explaining cache locality, and source of picture.

Question about slow graphics loop.

Code Review is a good place to get feedback on your code.

Game Development will give more game-based answers.