Flowing Fluid Registry Helper for Minecraft Forge 1.16

Fluids.java

public class FluidTest
{
	public static final DeferredRegister<Fluid> FLUIDS = DeferredRegister.create(ForgeRegistries.FLUIDS, "modid");
	
	public static final Pair<RegistryObject<ForgeFlowingFluid.Source>, RegistryObject<ForgeFlowingFluid.Flowing>> TEST_FLUIDS =
		registerFluid("test_fluid", "flowing_test_fluid",
      ForgeFlowingFluid.Source::new,
      ForgeFlowingFluid.Flowing::new,
		  FluidAttributes.builder(new ResourceLocation("modid:block/test_fluid_still"), new ResourceLocation("modid:block/test_fluid_flowing")));
	
	public static <SOURCE extends ForgeFlowingFluid.Source, FLOW extends ForgeFlowingFluid.Flowing>	// type args
		Pair<RegistryObject<SOURCE>, RegistryObject<FLOW>>	// return type
		registerFluid(String sourceName, String flowName,
			Function<ForgeFlowingFluid.Properties, SOURCE> sourceConstructor,
			Function<ForgeFlowingFluid.Properties, FLOW> flowConstructor,
			FluidAttributes.Builder attributes)
	{
		// make fake suppliers that will point to the registry objects later
		SupplierWrapper<SOURCE> sourceWrapper = new SupplierWrapper<>();
		SupplierWrapper<FLOW> flowWrapper = new SupplierWrapper<>();
		ForgeFlowingFluid.Properties props = new ForgeFlowingFluid.Properties(sourceWrapper, flowWrapper, attributes);
		RegistryObject<SOURCE> sourceObject = FLUIDS.register(sourceName, () -> sourceConstructor.apply(props));
		RegistryObject<FLOW> flowObject = FLUIDS.register(flowName, () -> flowConstructor.apply(props));
		// now that the registry objects exist, we can use them as the real suppliers
		sourceWrapper.setSupplier(sourceObject);
		flowWrapper.setSupplier(flowObject);
		return Pair.of(sourceObject, flowObject);
	}
	
	public static class SupplierWrapper<T> implements Supplier<T>
	{
		private Supplier<T> baseSupplier = null;
		
		// call this or ten thousand years dungeon
		public void setSupplier(Supplier<T> supplier)
		{
			this.baseSupplier = supplier;
		}
		
		@Override
		public T get()
		{
			Objects.requireNonNull(this.baseSupplier);
			return this.baseSupplier.get();
		}
		
	}
}