EntitySpawns 1.16.2 Cheat Sheet

EntitySpawnsCheatSheet.java

/*
MIT License

Copyright (c) 2020 CorgiTaco

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*/    
import com.google.common.collect.ImmutableMap;
import net.minecraft.entity.EntityClassification;
import net.minecraft.entity.EntityType;
import net.minecraft.util.registry.WorldGenRegistries;
import net.minecraft.world.biome.Biome;
import net.minecraft.world.biome.MobSpawnInfo;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;

public class EntitySpawnsCheatSheet {
    
    //Iterate through all registered biomes in the WorldGenRegistries.
    public static void addSpawnEntries() {
        for (Biome biome : WorldGenRegistries.field_243657_i) {
            if (biome.getCategory() != Biome.Category.NETHER && biome.getCategory() != Biome.Category.THEEND && biome.getCategory() != Biome.Category.NONE) {
                addMobSpawnToBiome(biome, EntityClassification.MONSTER, new MobSpawnInfo.Spawners(EntityType.ENDERMAN, 100, 100, 100));
            }
        }
    }

    //Add the normal info along with a list of "Spawners"
    public static void addMobSpawnToBiome(Biome biome, EntityClassification classification, MobSpawnInfo.Spawners... spawners) {
        convertImmutableSpawners(biome);
        //Copy the list of spawners that already exist for the given biome.
        List<MobSpawnInfo.Spawners> spawnersList = new ArrayList<>(biome.func_242433_b().field_242554_e.get(classification));
        //Add all the spawners within our list.
        spawnersList.addAll(Arrays.asList(spawners));
        //Overwrite the list for the given classification with the old list and our new entries.
        biome.func_242433_b().field_242554_e.put(classification, spawnersList);
    }

    //Convert the immutable map to a mutable HashMap in order for us to change the data stored in these maps
    private static void convertImmutableSpawners(Biome biome) {
        if (biome.func_242433_b().field_242554_e instanceof ImmutableMap) {
            biome.func_242433_b().field_242554_e = new HashMap<>(biome.func_242433_b().field_242554_e);
        }
    }
}

Might to include you need to AT field_242554_e public
public-f net.minecraft.world.biome.MobSpawnInfo field_242554_e #field_242554_e