Here is the code of the generator. There are no errors at all
package worldgen;
import java.util.Random;
import worldgen.feature.StructureRuinsmall;
import net.minecraft.world.World;
import net.minecraft.world.biome.BiomeGenBase;
import net.minecraft.world.chunk.IChunkProvider;
import cpw.mods.fml.common.IWorldGenerator;
public class worldgen implements IWorldGenerator {
@Override
public void generate(Random random, int chunkX, int chunkZ, World world,
IChunkProvider chunkGenerator, IChunkProvider chunkProvider) {
switch(world.provider.dimensionId){
case 0:
generateSurface(world, random, chunkX*16, chunkZ*16);
}
}
private void generateSurface(World world, Random random, int x, int z) {
BiomeGenBase biome = world.getWorldChunkManager().getBiomeGenAt(x, z);
if ((biome == BiomeGenBase.plains)){
for (int a = 0; a < 1; a++){
int i = x + random.nextInt(256);
int k = z + random.nextInt(256);
int j = world.getHeightValue(i, k);
new StructureRuinsmall().generate(world, random, i, k, j);
}
}
}
}