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System Info: Java 11 (OpenJDK 64-Bit Server VM 11.0.4+11) Host: Windows 10 10.0 (amd64)
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java.lang.ExceptionInInitializerError
        at net.minecraft.server.v1_16_R2.RegistryGeneration.b(SourceFile:52)
        at net.minecraft.server.v1_16_R2.RegistryGeneration.a(SourceFile:75)
        at java.base/java.util.LinkedHashMap.forEach(LinkedHashMap.java:684)
        at net.minecraft.server.v1_16_R2.RegistryGeneration.<clinit>(SourceFile:74)
        at net.minecraft.server.v1_16_R2.IRegistry.<clinit>(SourceFile:237)
        at net.minecraft.server.v1_16_R2.DispenserRegistry.init(DispenserRegistry.java:29)
        at net.minecraft.server.v1_16_R2.Main.main(Main.java:60)
        at org.bukkit.craftbukkit.Main.main(Main.java:276)
Caused by: java.lang.ClassCastException: class net.minecraft.server.v1_16_R2.BiomeSettingsMobs$c cannot be cast to class net.minecraft.server.v1_16_R2.BiomeSettingsMobs (net.minecraft.server.v1_16_R2.BiomeSettingsMobs$c and net.minecraft.server.v1_16_R2.BiomeSettingsMobs are in unnamed module of loader 'app')
        at net.minecraft.server.v1_16_R2.BiomeSettingsMobs$a$MobList.add(BiomeSettingsMobs.java:83)
        at net.minecraft.server.v1_16_R2.BiomeSettingsMobs$a.a(BiomeSettingsMobs.java:126)
        at net.minecraft.server.v1_16_R2.BiomeSettings.a(SourceFile:351)
        at net.minecraft.server.v1_16_R2.BiomesSettingsDefault.c(SourceFile:730)
        at net.minecraft.server.v1_16_R2.BiomeRegistry.<clinit>(SourceFile:17)
        ... 8 more