If you want the world to store the objects whichs positions are greater than the worlds size you just have to use another constructor for the world: Instead of World(int worldWidth, int worldHeight, int cellSize) use World(int worldWidth, int worldHeight, int cellSize, boolean bounded) If the last parameter is false the world will store everything that is out of the screen. To generate new objects you have to use your terain generator and create new objects if your character reaches the edge of the world. And also you have to move all of your objects to the left or right if the character reaches the edge of the world.

Yes that would be the case. But if you kan just delete all objects that fall out of the screen. Or if you don't want to remove them because then the world would look diferent you should save them not as objects but as files or strings in your programm. That would take much less ram.

Also i noticed that all the code for action for your blocks is in your blocks class's you could take out alot of this code to reduce lagg and put it it into other class's so that you dont have to have so many objects using resources when you could have one or two in exchange for maby less structured code

You have to write a method that gives all the important information of the object and you have to get the objects coordinates. To get the important information of the object you should overwrite the toString method of java.lang.Object. Then if you want to save the strings you should use a file writer because all the informations of the area is very much to save it in the ram.

Well I most times use java.util.List<E> or java.util.ArrayList<E> instead of arrays because lists haven't got a static size and you can use many methods of the class. Also a ArrayIndexOutOfBoundsException is not caused that easily. But if you have to save very much data you better use a file because otherwhise the ram Greenfoot uses will not be enought. You would have to run a very long time in one direction to cause a OutOfMemoryError but this could be the case.

@Game/maniac, I have created a scenario with a bounded world that appears like an unbounded side-scrolling world. It builds uncharted territories as they come into view that remain forever unchanged. I will post it if you wish to take a look. It is not finished as far as having scrollable objects moved or removed, but the idea is there. I will continue to build on it. I did get a chance to document it a bit also.