CustomChunkGenerator

public class CustomChunkGenerator extends ChunkGenerator {

    @Override
    public ChunkData generateChunkData(World world, Random random, int chunkX, int chunkZ, BiomeGrid biomeGrid) {

        int currentHeight;

        int heightDifference = 30;
        int minHeight = 40;

        ChunkData chunk = createChunkData(world);

        SimplexOctaveGenerator generator = new SimplexOctaveGenerator(new Random(world.getSeed()), 8);

        //How steep the terrain should be
        generator.setScale(0.008D);


        if (biomeGrid.getBiome(7, minHeight, 7) == Biome.MOUNTAINS) {
            generator.setScale(0.01D);
        }

        //Generate blocks
        for (int x = 0; x < 16; x++) {
            for (int z = 0; z < 16; z++) {

                Biome biome = biomeGrid.getBiome(x, minHeight, z);

                //Set bottom to bedrock
                chunk.setBlock(x, 0, z, Material.BEDROCK);

                currentHeight = (int) ((generator.noise(chunkX * 16 + x, chunkZ * 16 + z, 0.5D, 0.5D, true) + 1) * heightDifference + minHeight);

                //Replace ocean biomes with plains
                if (biome == Biome.OCEAN || biome == Biome.DEEP_OCEAN || biome == Biome.FROZEN_OCEAN || biome == Biome.DEEP_FROZEN_OCEAN
                        || biome == Biome.WARM_OCEAN || biome == Biome.DEEP_WARM_OCEAN || biome == Biome.COLD_OCEAN || biome == Biome.DEEP_COLD_OCEAN
                        || biome == Biome.LUKEWARM_OCEAN || biome == Biome.DEEP_LUKEWARM_OCEAN) {

                    biomeGrid.setBiome(x, z, Biome.PLAINS);
                }

                //Set water below water level and set biome to ocean
                if (currentHeight < 62) {
                    for (int i = currentHeight + 1; i < 63; i++) {
                        chunk.setBlock(x, i, z, Material.WATER);
                    }

                    biomeGrid.setBiome(x, z, Biome.OCEAN);

                    chunk.setBlock(x, currentHeight, z, Material.SAND);
                    chunk.setBlock(x, currentHeight - 1, z, Material.SAND);
                }

                else if (biome == Biome.DESERT || biome == Biome.DESERT_HILLS || biome == Biome.DESERT_LAKES) {
                    chunk.setBlock(x, currentHeight, z, Material.SAND);
                    chunk.setBlock(x, currentHeight - 1, z, Material.SANDSTONE);

                    if (random.nextBoolean()) {
                        chunk.setBlock(x, currentHeight - 2, z, Material.SANDSTONE);
                    }

                } else {
                    chunk.setBlock(x, currentHeight, z, Material.GRASS_BLOCK);
                    chunk.setBlock(x, currentHeight - 1, z, Material.DIRT);
                }

                //Set all blocks under ground to stone
                for (int i = currentHeight - 2; i > 0; i--) {
                    if (chunk.getType(x, i, z) == Material.AIR) {
                        chunk.setBlock(x, i, z, Material.STONE);
                    }
                }

            }
        }

        return chunk;

    }

    @Override
    public List<BlockPopulator> getDefaultPopulators(World world) {
        return Arrays.asList(new LakePopulator(),
                new GrassPopulator(), new TreePopulator(),
                new OrePopulator(), new CavePopulator(),
                new DesertPopulator());
    }


    @Override
    public Location getFixedSpawnLocation(World world, Random random) {
        int x = random.nextInt(200) - 100;
        int z = random.nextInt(200) - 100;
        int y = world.getHighestBlockYAt(x, z);
        return new Location(world, x, y, z);
    }
}