Add utility method for lazy initialized structure elements

src/main/java/com/gtnewhorizon/structurelib/structure/LazyStructureElement.java

@@ -0,0 +1,38 @@
+package com.gtnewhorizon.structurelib.structure;
+
+import net.minecraft.item.ItemStack;
+import net.minecraft.world.World;
+
+import java.util.function.Function;
+
+class LazyStructureElement<T> implements IStructureElementDeferred<T> {
+	private Function<T, IStructureElement<T>> to;
+	private IStructureElement<T> elem;
+
+	public LazyStructureElement(Function<T, IStructureElement<T>> to) {
+		this.to = to;
+	}
+
+	private IStructureElement<T> get(T t) {
+		if (to != null) {
+			elem = to.apply(t);
+			to = null;
+		}
+		return elem;
+	}
+
+	@Override
+	public boolean check(T t, World world, int x, int y, int z) {
+		return get(t).check(t, world, x, y, z);
+	}
+
+	@Override
+	public boolean placeBlock(T t, World world, int x, int y, int z, ItemStack trigger) {
+		return get(t).placeBlock(t, world, x, y, z, trigger);
+	}
+
+	@Override
+	public boolean spawnHint(T t, World world, int x, int y, int z, ItemStack trigger) {
+		return get(t).spawnHint(t, world, x, y, z, trigger);
+	}
+}

src/main/java/com/gtnewhorizon/structurelib/structure/StructureUtility.java

@@ -787,6 +787,28 @@ public class StructureUtility {
 
 	//region defer
 
+	/**
+	 * Similar to defer, but caches the first returned element returned and won't call it again.
+	 * Initialization is not thread safe.
+	 */
+	public static <T> IStructureElementDeferred<T> lazy(Supplier<IStructureElement<T>> to) {
+		if (to == null) {
+			throw new IllegalArgumentException();
+		}
+		return new LazyStructureElement<>(t -> to.get());
+	}
+
+	/**
+	 * Similar to defer, but caches the first returned element returned and won't call it again.
+	 * Initialization is not thread safe.
+	 */
+	public static <T> IStructureElementDeferred<T> lazy(Function<T, IStructureElement<T>> to) {
+		if (to == null) {
+			throw new IllegalArgumentException();
+		}
+		return new LazyStructureElement<>(to);
+	}
+
 	public static <T> IStructureElementDeferred<T> defer(Supplier<IStructureElement<T>> to) {
 		if (to == null) {
 			throw new IllegalArgumentException();
@@ -1414,4 +1436,5 @@ public class StructureUtility {
 		}
 		return shape;
 	}
+
 }