That's not my experience, though game development is certainly a niche and Java may not be the top choice for that.
You might sometimes have to reach for SoA-like structures and reference them via indices, at least for the core ECS, but for the rest you can easily use bog-standard Java -- not everything has to be "ultra-fast, specially written java", just certain hot loops.
Right. I didn’t started digging into it until I realized the application was clearly sluggish in certain scenarios. As I am doing this for fun I am going to see what kind of speed up I get in rust for this.
You might sometimes have to reach for SoA-like structures and reference them via indices, at least for the core ECS, but for the rest you can easily use bog-standard Java -- not everything has to be "ultra-fast, specially written java", just certain hot loops.