This is the best way to get an entity when the world and its UUID are known.
It is faster than Server.getEntity(UUID) because it does not have to iterate all worlds
This event is called when an entity receives knockback by another entity. The knockback can be modified in the event. If the event is cancelled the entity is not knocked back.
HashSet sometimes uses compareTo() instead of equals() and this breaks the comparison of net.minecraft.server.NextTickListEntry (the only place where HashTreeSet is used).
In this cases duplicate entries could be added to the HashSet of HashTreeSet, because NextTickListEntry.compareTo() does not return 0, even if NextTickListEntry.equals() returns true.
ObjectOpenHashSet never uses compareTo(), so the inconsistencies of NextTickListEntry cause no problems.
Fixes https://github.com/PaperMC/Paper/issues/588
Fixes falling dragon eggs in lazy chunks fall to the block below the last empty block and replacing that block with them.
See also https://bugs.mojang.com/browse/MC-94186
Brokkonaut