Instanced bogeys

src/main/java/com/simibubi/create/AllEntityTypes.java

@@ -16,8 +16,10 @@ import com.simibubi.create.content.curiosities.weapons.PotatoProjectileEntity;
 import com.simibubi.create.content.curiosities.weapons.PotatoProjectileRenderer;
 import com.simibubi.create.content.logistics.trains.entity.CarriageContraptionEntity;
 import com.simibubi.create.content.logistics.trains.entity.CarriageContraptionEntityRenderer;
+import com.simibubi.create.content.logistics.trains.entity.CarriageContraptionInstance;
 import com.simibubi.create.foundation.data.CreateEntityBuilder;
 import com.simibubi.create.foundation.utility.Lang;
+import com.tterrag.registrate.builders.EntityBuilder;
 import com.tterrag.registrate.util.entry.EntityEntry;
 import com.tterrag.registrate.util.nullness.NonNullConsumer;
 import com.tterrag.registrate.util.nullness.NonNullFunction;
@@ -33,15 +35,20 @@ import net.minecraft.world.entity.MobCategory;
 public class AllEntityTypes {
 
 	public static final EntityEntry<OrientedContraptionEntity> ORIENTED_CONTRAPTION = contraption("contraption",
-		OrientedContraptionEntity::new, () -> OrientedContraptionEntityRenderer::new, 5, 3, true);
+		OrientedContraptionEntity::new, () -> OrientedContraptionEntityRenderer::new, 5, 3, true)
+		.register();
 	public static final EntityEntry<ControlledContraptionEntity> CONTROLLED_CONTRAPTION =
 		contraption("stationary_contraption", ControlledContraptionEntity::new, () -> ContraptionEntityRenderer::new,
-			20, 40, false);
+			20, 40, false)
+		.register();
 	public static final EntityEntry<GantryContraptionEntity> GANTRY_CONTRAPTION = contraption("gantry_contraption",
-		GantryContraptionEntity::new, () -> ContraptionEntityRenderer::new, 10, 40, false);
+		GantryContraptionEntity::new, () -> ContraptionEntityRenderer::new, 10, 40, false)
+		.register();
 	public static final EntityEntry<CarriageContraptionEntity> CARRIAGE_CONTRAPTION =
 		contraption("carriage_contraption", CarriageContraptionEntity::new,
-			() -> CarriageContraptionEntityRenderer::new, 15, 3, true);
+			() -> CarriageContraptionEntityRenderer::new, 15, 3, true)
+		.instance(() -> CarriageContraptionInstance::new)
+		.register();
 
 	public static final EntityEntry<SuperGlueEntity> SUPER_GLUE =
 		register("super_glue", SuperGlueEntity::new, () -> SuperGlueRenderer::new, MobCategory.MISC, 10,
@@ -61,11 +68,11 @@ public class AllEntityTypes {
 
 	//
 
-	private static <T extends Entity> EntityEntry<T> contraption(String name, EntityFactory<T> factory,
+	private static <T extends Entity> CreateEntityBuilder<T, ?> contraption(String name, EntityFactory<T> factory,
 		NonNullSupplier<NonNullFunction<EntityRendererProvider.Context, EntityRenderer<? super T>>> renderer, int range,
 		int updateFrequency, boolean sendVelocity) {
 		return register(name, factory, renderer, MobCategory.MISC, range, updateFrequency, sendVelocity, true,
-			AbstractContraptionEntity::build).register();
+			AbstractContraptionEntity::build);
 	}
 
 	private static <T extends Entity> CreateEntityBuilder<T, ?> register(String name, EntityFactory<T> factory,

src/main/java/com/simibubi/create/content/contraptions/components/structureMovement/render/ContraptionGroup.java

@@ -16,7 +16,7 @@ public class ContraptionGroup<P extends ContraptionProgram> extends InstancedMat
 	}
 
 	@Override
-	public void setup(P program) {
+    protected void setup(P program) {
 		contraption.setup(program);
 	}
 

src/main/java/com/simibubi/create/content/logistics/trains/IBogeyBlock.java

@@ -6,8 +6,11 @@ import java.util.List;
 
 import javax.annotation.Nullable;
 
+import com.jozufozu.flywheel.api.MaterialManager;
 import com.mojang.blaze3d.vertex.PoseStack;
 import com.simibubi.create.content.contraptions.wrench.IWrenchable;
+import com.simibubi.create.content.logistics.trains.entity.BogeyInstance;
+import com.simibubi.create.content.logistics.trains.entity.CarriageBogey;
 
 import net.minecraft.client.renderer.MultiBufferSource;
 import net.minecraft.core.BlockPos;
@@ -43,6 +46,9 @@ public interface IBogeyBlock extends IWrenchable {
 	public void render(@Nullable BlockState state, float wheelAngle, PoseStack ms, float partialTicks,
 		MultiBufferSource buffers, int light, int overlay);
 
+	@OnlyIn(Dist.CLIENT)
+	public BogeyInstance createInstance(MaterialManager materialManager, CarriageBogey bogey);
+
 	public default Direction getBogeyUpDirection() {
 		return Direction.UP;
 	}

src/main/java/com/simibubi/create/content/logistics/trains/entity/BogeyInstance.java

@@ -0,0 +1,183 @@
+package com.simibubi.create.content.logistics.trains.entity;
+
+import com.jozufozu.flywheel.api.Material;
+import com.jozufozu.flywheel.api.MaterialManager;
+import com.jozufozu.flywheel.core.Materials;
+import com.jozufozu.flywheel.core.materials.model.ModelData;
+import com.mojang.blaze3d.vertex.PoseStack;
+import com.simibubi.create.AllBlockPartials;
+import com.simibubi.create.AllBlocks;
+import com.simibubi.create.content.contraptions.relays.elementary.ShaftBlock;
+import com.simibubi.create.foundation.render.CachedBufferer;
+import com.simibubi.create.foundation.utility.AngleHelper;
+import com.simibubi.create.foundation.utility.Iterate;
+
+import net.minecraft.core.Direction;
+
+public sealed class BogeyInstance {
+
+	public final CarriageBogey bogey;
+	private final ModelData[] shafts;
+
+	protected BogeyInstance(CarriageBogey bogey, MaterialManager materialManager) {
+		this.bogey = bogey;
+
+		shafts = new ModelData[2];
+
+		materialManager.defaultSolid()
+				.material(Materials.TRANSFORMED)
+				.getModel(AllBlocks.SHAFT.getDefaultState()
+						.setValue(ShaftBlock.AXIS, Direction.Axis.Z))
+				.createInstances(shafts);
+
+	}
+
+	public void remove() {
+		for (ModelData shaft : shafts)
+			shaft.delete();
+	}
+
+	public void beginFrame(float wheelAngle, PoseStack ms) {
+
+		for (int i : Iterate.zeroAndOne)
+			shafts[i].setTransform(ms)
+					.translate(-.5f, .25f, i * -1)
+					.centre()
+					.rotateZ(wheelAngle)
+					.unCentre();
+	}
+
+	public void updateLight(int blockLight, int skyLight) {
+		for (ModelData shaft : shafts) {
+			shaft.setBlockLight(blockLight).setSkyLight(skyLight);
+		}
+	}
+
+	public static final class Frame extends BogeyInstance {
+
+		private final ModelData frame;
+		private final ModelData[] wheels;
+
+		public Frame(CarriageBogey bogey, MaterialManager materialManager) {
+			super(bogey, materialManager);
+
+			frame = materialManager.defaultSolid()
+					.material(Materials.TRANSFORMED)
+					.getModel(AllBlockPartials.BOGEY_FRAME)
+					.createInstance();
+
+			wheels = new ModelData[2];
+
+			materialManager.defaultSolid()
+					.material(Materials.TRANSFORMED)
+					.getModel(AllBlockPartials.SMALL_BOGEY_WHEELS)
+					.createInstances(wheels);
+		}
+
+		@Override
+		public void beginFrame(float wheelAngle, PoseStack ms) {
+			super.beginFrame(wheelAngle, ms);
+
+			frame.setTransform(ms);
+
+			for (int side : Iterate.positiveAndNegative) {
+				wheels[(side + 1) / 2].setTransform(ms)
+						.translate(0, 12 / 16f, side)
+						.rotateX(wheelAngle);
+			}
+		}
+
+		@Override
+		public void updateLight(int blockLight, int skyLight) {
+			super.updateLight(blockLight, skyLight);
+			frame.setBlockLight(blockLight).setSkyLight(skyLight);
+			for (ModelData wheel : wheels)
+				wheel.setBlockLight(blockLight).setSkyLight(skyLight);
+		}
+
+		@Override
+		public void remove() {
+			super.remove();
+			frame.delete();
+			for (ModelData wheel : wheels)
+				wheel.delete();
+		}
+	}
+
+	public static final class Drive extends BogeyInstance {
+
+		private final ModelData[] secondShaft;
+		private final ModelData drive;
+		private final ModelData piston;
+		private final ModelData wheels;
+		private final ModelData pin;
+
+		public Drive(CarriageBogey bogey, MaterialManager materialManager) {
+			super(bogey, materialManager);
+			Material<ModelData> mat = materialManager.defaultSolid()
+					.material(Materials.TRANSFORMED);
+
+			secondShaft = new ModelData[2];
+
+			mat.getModel(AllBlocks.SHAFT.getDefaultState()
+							.setValue(ShaftBlock.AXIS, Direction.Axis.X))
+					.createInstances(secondShaft);
+
+			drive = mat.getModel(AllBlockPartials.BOGEY_DRIVE)
+					.createInstance();
+			piston = mat.getModel(AllBlockPartials.BOGEY_PISTON)
+					.createInstance();
+			wheels = mat.getModel(AllBlockPartials.LARGE_BOGEY_WHEELS)
+					.createInstance();
+			pin = mat.getModel(AllBlockPartials.BOGEY_PIN)
+					.createInstance();
+		}
+
+		@Override
+		public void beginFrame(float wheelAngle, PoseStack ms) {
+			super.beginFrame(wheelAngle, ms);
+
+			for (int i : Iterate.zeroAndOne)
+				secondShaft[i].setTransform(ms)
+						.translate(-.5f, .25f, .5f + i * -2)
+						.centre()
+						.rotateX(wheelAngle)
+						.unCentre();
+
+			drive.setTransform(ms);
+			piston.setTransform(ms)
+					.translate(0, 0, 1 / 4f * Math.sin(AngleHelper.rad(wheelAngle)));
+
+			wheels.setTransform(ms)
+					.translate(0, 1, 0)
+					.rotateX(wheelAngle);
+			pin.setTransform(ms)
+					.translate(0, 1, 0)
+					.rotateX(wheelAngle)
+					.translate(0, 1 / 4f, 0)
+					.rotateX(-wheelAngle);
+		}
+
+		@Override
+		public void updateLight(int blockLight, int skyLight) {
+			super.updateLight(blockLight, skyLight);
+			for (ModelData shaft : secondShaft)
+				shaft.setBlockLight(blockLight).setSkyLight(skyLight);
+			drive.setBlockLight(blockLight).setSkyLight(skyLight);
+			piston.setBlockLight(blockLight).setSkyLight(skyLight);
+			wheels.setBlockLight(blockLight).setSkyLight(skyLight);
+			pin.setBlockLight(blockLight).setSkyLight(skyLight);
+		}
+
+		@Override
+		public void remove() {
+			super.remove();
+			for (ModelData shaft : secondShaft)
+				shaft.delete();
+			drive.delete();
+			piston.delete();
+			wheels.delete();
+			pin.delete();
+		}
+	}
+}

src/main/java/com/simibubi/create/content/logistics/trains/entity/Carriage.java

@@ -63,6 +63,7 @@ public class Carriage {
 
 		updateContraptionAnchors();
 
+		bogey1.setLeading();
 		bogey1.carriage = this;
 		if (bogey2 != null)
 			bogey2.carriage = this;

src/main/java/com/simibubi/create/content/logistics/trains/entity/CarriageBogey.java

@@ -2,6 +2,7 @@ package com.simibubi.create.content.logistics.trains.entity;
 
 import javax.annotation.Nullable;
 
+import com.jozufozu.flywheel.api.MaterialManager;
 import com.simibubi.create.Create;
 import com.simibubi.create.content.logistics.trains.IBogeyBlock;
 import com.simibubi.create.content.logistics.trains.TrackGraph;
@@ -24,6 +25,8 @@ public class CarriageBogey {
 
 	public Carriage carriage;
 
+	boolean isLeading;
+
 	IBogeyBlock type;
 	Couple<TravellingPoint> points;
 
@@ -133,4 +136,11 @@ public class CarriageBogey {
 		return carriageBogey;
 	}
 
-}
+	public BogeyInstance createInstance(MaterialManager materialManager) {
+		return type.createInstance(materialManager, this);
+	}
+
+	void setLeading() {
+		isLeading = true;
+	}
+}

src/main/java/com/simibubi/create/content/logistics/trains/entity/CarriageContraptionEntityRenderer.java

@@ -1,5 +1,6 @@
 package com.simibubi.create.content.logistics.trains.entity;
 
+import com.jozufozu.flywheel.backend.Backend;
 import com.jozufozu.flywheel.util.transform.TransformStack;
 import com.mojang.blaze3d.vertex.PoseStack;
 import com.simibubi.create.content.contraptions.components.structureMovement.ContraptionEntityRenderer;
@@ -33,6 +34,8 @@ public class CarriageContraptionEntityRenderer extends ContraptionEntityRenderer
 		MultiBufferSource buffers, int overlay) {
 		super.render(entity, yaw, partialTicks, ms, buffers, overlay);
 
+		if (Backend.isOn()) return;
+
 		Carriage carriage = entity.getCarriage();
 		if (carriage == null)
 			return;
@@ -40,8 +43,8 @@ public class CarriageContraptionEntityRenderer extends ContraptionEntityRenderer
 		Vec3 position = entity.getPosition(partialTicks);
 
 		ms.pushPose();
-		carriage.bogeys.forEachWithContext((bogey, first) -> {
-			if (!first && !carriage.isOnTwoBogeys())
+		carriage.bogeys.forEach(bogey -> {
+			if (bogey == null)
 				return;
 
 			ms.pushPose();
@@ -52,7 +55,7 @@ public class CarriageContraptionEntityRenderer extends ContraptionEntityRenderer
 				.rotateY(viewYRot + 90)
 				.rotateX(-viewXRot)
 				.rotateY(180)
-				.translate(0, 0, first ? 0 : -bogeySpacing)
+				.translate(0, 0, bogey.isLeading ? 0 : -bogeySpacing)
 				.rotateY(-180)
 				.rotateX(viewXRot)
 				.rotateY(-viewYRot - 90)
@@ -62,9 +65,9 @@ public class CarriageContraptionEntityRenderer extends ContraptionEntityRenderer
 
 			bogey.type.render(null, bogey.wheelAngle.getValue(partialTicks), ms, partialTicks, buffers,
 				getPackedLightCoords(entity, partialTicks), overlay);
-			bogey.updateCouplingAnchor(position, viewXRot, viewYRot, bogeySpacing, partialTicks, first);
+			bogey.updateCouplingAnchor(position, viewXRot, viewYRot, bogeySpacing, partialTicks, bogey.isLeading);
 			if (!carriage.isOnTwoBogeys())
-				bogey.updateCouplingAnchor(position, viewXRot, viewYRot, bogeySpacing, partialTicks, !first);
+				bogey.updateCouplingAnchor(position, viewXRot, viewYRot, bogeySpacing, partialTicks, !bogey.isLeading);
 
 			ms.popPose();
 		});

src/main/java/com/simibubi/create/content/logistics/trains/entity/CarriageContraptionInstance.java

@@ -0,0 +1,101 @@
+package com.simibubi.create.content.logistics.trains.entity;
+
+import com.jozufozu.flywheel.api.MaterialManager;
+import com.jozufozu.flywheel.api.instance.DynamicInstance;
+import com.jozufozu.flywheel.backend.instancing.entity.EntityInstance;
+import com.jozufozu.flywheel.util.AnimationTickHolder;
+import com.jozufozu.flywheel.util.transform.TransformStack;
+import com.mojang.blaze3d.vertex.PoseStack;
+import com.simibubi.create.foundation.utility.Couple;
+
+import net.minecraft.client.renderer.LightTexture;
+import net.minecraft.core.BlockPos;
+import net.minecraft.world.level.LightLayer;
+import net.minecraft.world.phys.Vec3;
+
+public class CarriageContraptionInstance extends EntityInstance<CarriageContraptionEntity> implements DynamicInstance {
+
+	private final PoseStack ms = new PoseStack();
+
+	private Carriage carriage;
+	private Couple<BogeyInstance> bogeys;
+
+	public CarriageContraptionInstance(MaterialManager materialManager, CarriageContraptionEntity entity) {
+		super(materialManager, entity);
+	}
+
+	@Override
+	public void init() {
+		carriage = entity.getCarriage();
+
+		if (carriage == null) return;
+
+		bogeys = carriage.bogeys.mapNotNullWithParam(CarriageBogey::createInstance, materialManager);
+		updateLight();
+	}
+
+	@Override
+	public void beginFrame() {
+		if (bogeys == null) {
+			init();
+			return;
+		}
+
+		float partialTicks = AnimationTickHolder.getPartialTicks();
+
+		float viewYRot = entity.getViewYRot(partialTicks);
+		float viewXRot = entity.getViewXRot(partialTicks);
+		int bogeySpacing = carriage.bogeySpacing;
+
+		ms.pushPose();
+
+		TransformStack.cast(ms)
+				.translate(getInstancePosition(partialTicks))
+				.translate(0, -1.5 - 1 / 128f, 0);;
+
+		for (BogeyInstance instance : bogeys) {
+			if (instance != null) {
+				ms.pushPose();
+				CarriageBogey bogey = instance.bogey;
+
+				TransformStack.cast(ms)
+						.rotateY(viewYRot + 90)
+						.rotateX(-viewXRot)
+						.rotateY(180)
+						.translate(0, 0, bogey.isLeading ? 0 : -bogeySpacing)
+						.rotateY(-180)
+						.rotateX(viewXRot)
+						.rotateY(-viewYRot - 90)
+						.rotateY(bogey.yaw.getValue(partialTicks))
+						.rotateX(bogey.pitch.getValue(partialTicks))
+						.translate(0, .5f, 0);
+
+				instance.beginFrame(bogey.wheelAngle.getValue(partialTicks), ms);
+				ms.popPose();
+			}
+		}
+
+		ms.popPose();
+	}
+
+	@Override
+	public void updateLight() {
+		if (bogeys == null) return;
+
+		var pos = new BlockPos(entity.getLightProbePosition(AnimationTickHolder.getPartialTicks()));
+		int block = world.getBrightness(LightLayer.BLOCK, pos);
+		int sky = world.getBrightness(LightLayer.SKY, pos);
+
+		bogeys.forEach(instance -> {
+			if (instance != null)
+				instance.updateLight(block, sky);
+		});
+	}
+
+	@Override
+	public void remove() {
+		bogeys.forEach(BogeyInstance::remove);
+	}
+
+
+}

src/main/java/com/simibubi/create/content/logistics/trains/track/StandardBogeyBlock.java

@@ -2,6 +2,7 @@ package com.simibubi.create.content.logistics.trains.track;
 
 import java.util.EnumSet;
 
+import com.jozufozu.flywheel.api.MaterialManager;
 import com.mojang.blaze3d.vertex.PoseStack;
 import com.mojang.blaze3d.vertex.VertexConsumer;
 import com.mojang.math.Vector3f;
@@ -10,6 +11,8 @@ import com.simibubi.create.AllBlocks;
 import com.simibubi.create.AllTileEntities;
 import com.simibubi.create.content.contraptions.relays.elementary.ShaftBlock;
 import com.simibubi.create.content.logistics.trains.IBogeyBlock;
+import com.simibubi.create.content.logistics.trains.entity.BogeyInstance;
+import com.simibubi.create.content.logistics.trains.entity.CarriageBogey;
 import com.simibubi.create.foundation.block.ITE;
 import com.simibubi.create.foundation.render.CachedBufferer;
 import com.simibubi.create.foundation.utility.AngleHelper;
@@ -36,7 +39,7 @@ import net.minecraftforge.api.distmarker.OnlyIn;
 public class StandardBogeyBlock extends Block implements IBogeyBlock, ITE<StandardBogeyTileEntity> {
 
 	public static final EnumProperty<Axis> AXIS = BlockStateProperties.HORIZONTAL_AXIS;
-	private boolean large;
+	private final boolean large;
 
 	public StandardBogeyBlock(Properties p_i48440_1_, boolean large) {
 		super(p_i48440_1_);
@@ -114,23 +117,30 @@ public class StandardBogeyBlock extends Block implements IBogeyBlock, ITE<Standa
 				.light(light)
 				.renderInto(ms, vb);
 
-		if (!large) {
-			CachedBufferer.partial(AllBlockPartials.BOGEY_FRAME, air)
+		if (large) {
+			renderLargeBogey(wheelAngle, ms, light, vb, air);
+		} else {
+			renderBogey(wheelAngle, ms, light, vb, air);
+		}
+	}
+
+	private void renderBogey(float wheelAngle, PoseStack ms, int light, VertexConsumer vb, BlockState air) {
+		CachedBufferer.partial(AllBlockPartials.BOGEY_FRAME, air)
+			.light(light)
+			.renderInto(ms, vb);
+
+		for (int side : Iterate.positiveAndNegative) {
+			ms.pushPose();
+			CachedBufferer.partial(AllBlockPartials.SMALL_BOGEY_WHEELS, air)
+				.translate(0, 12 / 16f, side)
+				.rotateX(wheelAngle)
 				.light(light)
 				.renderInto(ms, vb);
-
-			for (int side : Iterate.positiveAndNegative) {
-				ms.pushPose();
-				CachedBufferer.partial(AllBlockPartials.SMALL_BOGEY_WHEELS, air)
-					.translate(0, 12 / 16f, side)
-					.rotateX(wheelAngle)
-					.light(light)
-					.renderInto(ms, vb);
-				ms.popPose();
-			}
-			return;
+			ms.popPose();
 		}
+	}
 
+	private void renderLargeBogey(float wheelAngle, PoseStack ms, int light, VertexConsumer vb, BlockState air) {
 		for (int i : Iterate.zeroAndOne)
 			CachedBufferer.block(AllBlocks.SHAFT.getDefaultState()
 				.setValue(ShaftBlock.AXIS, Axis.X))
@@ -163,18 +173,23 @@ public class StandardBogeyBlock extends Block implements IBogeyBlock, ITE<Standa
 			.light(light)
 			.renderInto(ms, vb);
 		ms.popPose();
+	}
 
+	@Override
+	public BogeyInstance createInstance(MaterialManager materialManager, CarriageBogey bogey) {
+		if (large) {
+			return new BogeyInstance.Drive(bogey, materialManager);
+		} else {
+			return new BogeyInstance.Frame(bogey, materialManager);
+		}
 	}
 
 	@Override
 	public BlockState rotate(BlockState pState, Rotation pRotation) {
-		switch (pRotation) {
-		case COUNTERCLOCKWISE_90:
-		case CLOCKWISE_90:
-			return pState.cycle(AXIS);
-		default:
-			return pState;
-		}
+		return switch (pRotation) {
+			case COUNTERCLOCKWISE_90, CLOCKWISE_90 -> pState.cycle(AXIS);
+			default -> pState;
+		};
 	}
 
 	@Override

src/main/java/com/simibubi/create/foundation/data/CreateEntityBuilder.java

@@ -42,7 +42,7 @@ public class CreateEntityBuilder<T extends Entity, P> extends EntityBuilder<T, P
 	}
 
 	public CreateEntityBuilder<T, P> instance(NonNullSupplier<BiFunction<MaterialManager, T, EntityInstance<? super T>>> instanceFactory, boolean renderNormally) {
-		return instance(instanceFactory, be -> true);
+		return instance(instanceFactory, be -> renderNormally);
 	}
 
 	public CreateEntityBuilder<T, P> instance(NonNullSupplier<BiFunction<MaterialManager, T, EntityInstance<? super T>>> instanceFactory, NonNullPredicate<T> renderNormally) {

src/main/java/com/simibubi/create/foundation/utility/Couple.java

@@ -63,10 +63,15 @@ public class Couple<T> extends Pair<T, T> implements Iterable<T> {
 		return Couple.create(function.apply(first, values.first), function.apply(second, values.second));
 	}
 
+	public <S, R> Couple<S> mapNotNullWithParam(BiFunction<T, R, S> function, R value) {
+		return Couple.create(first != null ? function.apply(first, value) : null,
+				second != null ? function.apply(second, value) : null);
+	}
+
 	public boolean both(Predicate<T> test) {
 		return test.test(getFirst()) && test.test(getSecond());
 	}
-	
+
 	public boolean either(Predicate<T> test) {
 		return test.test(getFirst()) || test.test(getSecond());
 	}
@@ -125,7 +130,7 @@ public class Couple<T> extends Pair<T, T> implements Iterable<T> {
 	private static class Couplerator<T> implements Iterator<T> {
 
 		int state;
-		private Couple<T> couple;
+		private final Couple<T> couple;
 
 		public Couplerator(Couple<T> couple) {
 			this.couple = couple;