@GotoLink
I know that I am not able to reference a non-static method in a static context normally but I do know there's a way to manage this, as I think this is the method they used for the setBlock Command of CommandBlocks in 1.7.2.
If I am wrong and am using the wrong method I just want to know which method I gotta use in order to place a block at a position.
@Draco18s
I know it's not the same.
world.setBlock() cannot be resolved, therefore World.setBlock() is the right option.
I was just a little careless with the problem-description, sorry for that.