This error was fixed by reinstalling Java, both JRE and JDK. I also installed Gradle, if reinstalling this doesn't work.

 

After building the code in Eclipse and trying to start a new world, everything crashes.

For some reason a Superflat doesn't crash, so I suspect it's a problem with world generator.

 

 

 

Logs:

 

 

[20:44:12] [server thread/ERROR]: Encountered an unexpected exception

 

 

java.lang.IllegalAccessError: tried to access field net.minecraft.util.WeightedRandom$Item.itemWeight from class net.minecraft.item.Item

at net.minecraft.item.Item.getChestGenBase(Item.java:1045) ~[item.class:?]

at net.minecraftforge.common.ChestGenHooks.getItems(ChestGenHooks.java:209) ~[ChestGenHooks.class:?]

at net.minecraft.world.gen.structure.StructureMineshaftPieces$Corridor.addComponentParts(StructureMineshaftPieces.java:678) ~[structureMineshaftPieces$Corridor.class:?]

at net.minecraft.world.gen.structure.StructureStart.generateStructure(StructureStart.java:46) ~[structureStart.class:?]

at net.minecraft.world.gen.structure.MapGenStructure.generateStructuresInChunk(MapGenStructure.java:95) ~[MapGenStructure.class:?]

at net.minecraft.world.gen.ChunkProviderGenerate.populate(ChunkProviderGenerate.java:395) ~[ChunkProviderGenerate.class:?]

at net.minecraft.world.gen.ChunkProviderServer.populate(ChunkProviderServer.java:230) ~[ChunkProviderServer.class:?]

at net.minecraft.world.chunk.Chunk.populateChunk(Chunk.java:1089) ~[Chunk.class:?]

at net.minecraft.world.gen.ChunkProviderServer.loadChunk(ChunkProviderServer.java:136) ~[ChunkProviderServer.class:?]

at net.minecraft.server.MinecraftServer.initialWorldChunkLoad(MinecraftServer.java:289) ~[MinecraftServer.class:?]

at net.minecraft.server.integrated.IntegratedServer.loadAllWorlds(IntegratedServer.java:79) ~[integratedServer.class:?]

at net.minecraft.server.integrated.IntegratedServer.startServer(IntegratedServer.java:94) ~[integratedServer.class:?]

at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:412) [MinecraftServer.class:?]

at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:705) [MinecraftServer$2.class:?]

[20:44:12] [server thread/ERROR]: This crash report has been saved to: D:\Java\172Forge\eclipse\.\crash-reports\crash-2013-12-30_20.44.12-server.txt

[20:44:12] [server thread/INFO]: Stopping server

[20:44:12] [server thread/INFO]: Saving players

[20:44:12] [server thread/INFO]: Saving worlds

[20:44:12] [server thread/INFO]: Saving chunks for level 'New World'/Overworld

[20:44:13] [server thread/INFO]: Saving chunks for level 'New World'/Nether

[20:44:13] [server thread/INFO]: Saving chunks for level 'New World'/The End

[20:44:15] [server thread/INFO]: Unloading dimension 0

[20:44:15] [server thread/INFO]: Unloading dimension -1

[20:44:15] [server thread/INFO]: Unloading dimension 1

[20:44:15] [server thread/INFO]: The state engine was in incorrect state SERVER_STARTING and forced into state SERVER_STOPPED. Errors may have been discarded.

---- Minecraft Crash Report ----

// Hey, that tickles! Hehehe!

 

Time: 30.12.13 20:44

Description: Exception in server tick loop

 

java.lang.IllegalAccessError: tried to access field net.minecraft.util.WeightedRandom$Item.itemWeight from class net.minecraft.item.Item

at net.minecraft.item.Item.getChestGenBase(Item.java:1045)

at net.minecraftforge.common.ChestGenHooks.getItems(ChestGenHooks.java:209)

at net.minecraft.world.gen.structure.StructureMineshaftPieces$Corridor.addComponentParts(StructureMineshaftPieces.java:678)

at net.minecraft.world.gen.structure.StructureStart.generateStructure(StructureStart.java:46)

at net.minecraft.world.gen.structure.MapGenStructure.generateStructuresInChunk(MapGenStructure.java:95)

at net.minecraft.world.gen.ChunkProviderGenerate.populate(ChunkProviderGenerate.java:395)

at net.minecraft.world.gen.ChunkProviderServer.populate(ChunkProviderServer.java:230)

at net.minecraft.world.chunk.Chunk.populateChunk(Chunk.java:1089)

at net.minecraft.world.gen.ChunkProviderServer.loadChunk(ChunkProviderServer.java:136)

at net.minecraft.server.MinecraftServer.initialWorldChunkLoad(MinecraftServer.java:289)

at net.minecraft.server.integrated.IntegratedServer.loadAllWorlds(IntegratedServer.java:79)

at net.minecraft.server.integrated.IntegratedServer.startServer(IntegratedServer.java:94)

at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:412)

at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:705)

 

 

A detailed walkthrough of the error, its code path and all known details is as follows:

---------------------------------------------------------------------------------------

 

-- System Details --

Details:

Minecraft Version: 1.7.2

Operating System: Windows 7 (amd64) version 6.1

Java Version: 1.7.0_45, Oracle Corporation

Java VM Version: Java HotSpot 64-Bit Server VM (mixed mode), Oracle Corporation

Memory: 774535736 bytes (738 MB) / 1038876672 bytes (990 MB) up to 1038876672 bytes (990 MB)

JVM Flags: 3 total; -Xincgc -Xmx1024M -Xms1024M

AABB Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used

IntCache: cache: 0, tcache: 0, allocated: 13, tallocated: 95

FML: MCP v9.01-pre FML v7.2.28.976 Minecraft Forge 10.12.0.976 4 mods loaded, 4 mods active

mcp{8.09} [Minecraft Coder Pack] (minecraft.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available

FML{7.2.28.976} [Forge Mod Loader] (deobfuscated-bin.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available

Forge{10.12.0.976} [Minecraft Forge] (deobfuscated-bin.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available

examplemod{1.0} [Example Mod] (bin) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available

Profiler Position: N/A (disabled)

Vec3 Pool Size: 0 (0 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used

Player Count: 0 / 8; []

Type: Integrated Server (map_client.txt)

Is Modded: Definitely; Client brand changed to 'fml,forge'

#@!@# Game crashed! Crash report saved to: #@!@# .\crash-reports\crash-2013-12-30_20.44.12-server.txt

[20:44:16] [Client Shutdown Thread/INFO]: Stopping server

[20:44:16] [Client Shutdown Thread/INFO]: Saving players

[20:44:16] [Client Shutdown Thread/INFO]: Saving worlds

AL lib: (EE) alc_cleanup: 1 device not closed

 

 

This field (WeightedRandom$Item.itemWeight) is marked as protected in the source I have from MCP (both alpha and beta), so I went to see what Forge changes in functionality that it accesses that field. Weirdly enough, it is marked public in my Forge dev workspace I got through Gradle. I wanted to help you, but got more confused instead

I'm getting this too

 

This error was fixed by reinstalling Java, both JRE and JDK.

 

If this still doesn't work for you, know that I also installed gradle.