I have a custom biome, and I want to add custom features to it. however, using ".withFeature()", in the biome generation settings isn't working, because the biome gets initialized before the features does, giving me a Null Pointer Exception

 

Biome (gets initialized through a deferred register):

@Mod.EventBusSubscriber(modid = Main.MOD_ID, bus = Mod.EventBusSubscriber.Bus.MOD)
public class ModBiomes {

    public static final DeferredRegister<Biome> BIOMES = DeferredRegister.create(ForgeRegistries.BIOMES, Main.MOD_ID);

    public static final RegistryObject<Biome> EFFETE_FOREST = BIOMES.register("effete_forest", Maker::EffeteForest);

    @SubscribeEvent
    public static void setupBiomes(FMLCommonSetupEvent event) {
        event.enqueueWork(() ->
            setupBiome(EFFETE_FOREST.get(), BiomeManager.BiomeType.WARM, 10000000, //1000
                Type.NETHER, Type.FOREST, Type.HOT, Type.DRY)
        );
    }

    private static void setupBiome(Biome biome, BiomeManager.BiomeType type, int weight, Type... types) {
        RegistryKey<Biome> key = RegistryKey.getOrCreateKey(
            ForgeRegistries.Keys.BIOMES,
            Objects.requireNonNull(ForgeRegistries.BIOMES.getKey(biome), "Biome registry name was null")
        );

        BiomeDictionary.addTypes(key, types);
        BiomeManager.addBiome(type, new BiomeManager.BiomeEntry(key, weight));
    }

    private static class Maker {

        private static Biome EffeteForest() {
            BiomeGenerationSettings genset = new BiomeGenerationSettings.Builder()
                .withFeature(GenerationStage.Decoration.VEGETAL_DECORATION, ModFeatures.EFFETE_STEM_CONFIG)
              	// Above line gives a null pointer exception since EFFETE_STEM_CONFIG hasn't been initialized yet
                .withFeature(GenerationStage.Decoration.VEGETAL_DECORATION, Features.RED_MUSHROOM_NETHER)
                .withFeature(GenerationStage.Decoration.VEGETAL_DECORATION, Features.NETHER_SPROUTS)
                .withFeature(GenerationStage.Decoration.UNDERGROUND_ORES, Features.ORE_GOLD_NETHER)
                .withFeature(GenerationStage.Decoration.UNDERGROUND_ORES, Features.ORE_QUARTZ_NETHER)
                .withStructure(StructureFeatures.BASTION_REMNANT)
                .withStructure(StructureFeatures.NETHER_FOSSIL)
                .withStructure(StructureFeatures.RUINED_PORTAL_NETHER)
                .withSurfaceBuilder(ModConfiguredSurfaceBuilders.EFFETE_SURFACE_BUILDER)
                .build();

            MobSpawnInfo mobspawn = new MobSpawnInfo.Builder()
                .withSpawner(EntityClassification.MONSTER, new MobSpawnInfo.Spawners(EntityType.CAT, 4, 2, 4))
                .copy();


            BiomeAmbience ambience = new BiomeAmbience.Builder()
                .withGrassColor(0xDA67C1)
                .setFogColor(0xEEEEEE)
                .setWaterColor(0xCF21B8)
                .setWaterFogColor(0xCF78C5)
                .withSkyColor(0xE83452)
                .withFoliageColor(0xCA57C1)
                .build();

            return new Biome.Builder()
                .category(Biome.Category.NETHER)
                .withTemperatureModifier(Biome.TemperatureModifier.NONE)
                .withGenerationSettings(genset)
                .withMobSpawnSettings(mobspawn)
                .depth(0.09f)
                .scale(0.2f)
                .downfall(0.1f)
                .precipitation(Biome.RainType.NONE)
                .temperature(1.1f)
                .setEffects(ambience)
                .build();
        }
    }

}

 

Feature (gets initialized in Common setup):

@Mod.EventBusSubscriber(modid = Main.MOD_ID, bus = Mod.EventBusSubscriber.Bus.MOD)
public class ModFeatures {

    public static ConfiguredFeature<?, ?> EFFETE_STEM_CONFIG;

    @SubscribeEvent
    public static void setup(FMLCommonSetupEvent e) {
        EFFETE_STEM_CONFIG = register("effete_stem_feature",
            Feature.RANDOM_PATCH
                .withConfiguration(
                    (new BlockClusterFeatureConfig.Builder(
                        new SimpleBlockStateProvider(ModBlocks.EFFETE_STEM.get().getDefaultState()),
                        new EffeteColumnBlockPlacer(1, 2)
                    )).tries(3).ySpread(0).func_227317_b_().build()
                ).withPlacement(
                    Placement.COUNT_MULTILAYER.configure(new FeatureSpreadConfig(5)).square()
                )
        );
    }

    private static <FC extends IFeatureConfig> ConfiguredFeature<FC, ?> register(String key, ConfiguredFeature<FC, ?> configuredFeature) {
        return Registry.register(WorldGenRegistries.CONFIGURED_FEATURE, key, configuredFeature);
    }
}

 

You should register your features inside their apposite registry event. Also, there is another version of the BiomeGenerationSettings.Builder#withFeature method that takes in a Supplier<ConfiguredFeature<?, ?>>. You can look here to see an example on registering custom biomes with their custom features: https://github.com/Beethoven92/BetterEndForge/blob/master/src/main/java/mod/beethoven92/betterendforge/BetterEnd.java