public class TestChunkGenerator extends ChunkGenerator {

    @Override
    public boolean shouldGenerateBedrock() {
        return true;
    }

    @Override
    public boolean shouldGenerateDecorations() {
        return true;
    }

    @Override
    public boolean shouldGenerateNoise() {
        return true;
    }

    @Override
    public boolean shouldGenerateSurface() {
        return true;
    }

    @Override
    public boolean shouldGenerateCaves() {
        return false;
    }

    @Override
    public boolean shouldGenerateStructures() {
        return false;
    }
    
    @Override
    public boolean shouldGenerateMobs() {
        return true;
    }
}

        WorldCreator creator = new WorldCreator("TestWorld");
        creator.generator(new TestChunkGenerator());
        world = creator.createWorld();