IGraveCapability

    public interface IGraveCapability
    {
        Block getGraveBlock();
        void setGraveBlock(Block block);
        NBTTagCompound getGraveTag();
        void setGraveTag(NBTTagCompound tag);
        boolean hasTag();
    }

    public static class Storage implements IStorage<IGraveCapability>
    {
        @Override
        public NBTBase writeNBT(Capability<IGraveCapability> capability, IGraveCapability instance, EnumFacing side) {
            NBTTagCompound tagCompound = new NBTTagCompound();
            tagCompound.setString("graveBlock", ForgeRegistries.BLOCKS.getKey(instance.getGraveBlock()).toString());
            if (instance.getGraveTag() != null)
                tagCompound.setTag("graveTag", instance.getGraveTag());
            return tagCompound;
        }

        @Override
        public void readNBT(Capability<IGraveCapability> capability, IGraveCapability instance, EnumFacing side, NBTBase nbt) {
            instance.setGraveBlock(ForgeRegistries.BLOCKS.getValue(new ResourceLocation(((NBTTagCompound)nbt).getString("graveBlock"))));
            if (((NBTTagCompound) nbt).hasKey("graveTag"))
                instance.setGraveTag(((NBTTagCompound)nbt).getCompoundTag("graveTag"));
        }
    }

    public static class DefaultImpl implements IGraveCapability
    {
        NBTTagCompound graveTag;
        Block graveBlock;

        @Override
        public NBTTagCompound getGraveTag()
        {
            return graveTag;
        }

        @Override
        public void setGraveTag(NBTTagCompound chiselAndBitsGrave)
        {
            this.graveTag = chiselAndBitsGrave;
        }

        @Override
        public boolean hasTag()
        {
            return graveTag != null;
        }

        @Override
        public Block getGraveBlock()
        {
            return graveBlock;
        }

        @Override
        public void setGraveBlock(Block block)
        {
            graveBlock = block;
        }
    }