Sahel

I need a collection of currently loaded chunks that can be iterated over to check if they contain one of my custom mobs. I tried creating a public static ArrayList and adding and subtracting from it on ChunkEvent.Load and ChunkEvent.Unload respectively, but it keeps throwing a ConcurrentModificationException error, despite me not modifying it while I'm iterating over it. I *believe* this could be caused by two Chunk.Load events firing simultaneously, although I'm admittedly not enough of an expert into Minecraft's internal mechanics to know if this is the case or not. Regardless, if there is a more straightforward way of getting all the currently loaded chunks, I would like to know it.

In case anyone comes along with a similar issue, I'll write down what I did to set my structure's orientation and put it here: I wrote my own structure by extending the Structure class. It has a findGenerationPoint() that utilizes a custom placement class (that is very similar to the JigsawPlacement class). The custom placement class's addPieces() is exactly the same as JigsawPlacement.addpieces() except that it takes rotation as a parameter and uses that to replace the random rotation that the JigsawPlacement.addPieces() method uses. Thanks for pointing me in the right direction, warjort. Without your help, I'd probably still be fiddling around with PoolElementStructurePiece, to no avail.

I've made a custom structure and need it to generate facing North. However, the JSON files for custom structures do not allow me to set this feature. Is there another way I can go about doing this? I've looked at some of the vanilla structure generation information in net.minecraft.world.level.levelgen.structure, and, while I found a "rotation" field in the PoolElementStructurePiece class, I'm unsure how I would use it (as it appears to interface with NBT files), or if this is even the proper class/field to use for my purposes. Any direction would be helpful here.