Ensure supplier don't materialize more than once

3 files changed, 38 insertions, 4 deletions

diff --git a/BJC-Utils2/src/main/java/bjc/utils/data/Lazy.java b/BJC-Utils2/src/main/java/bjc/utils/data/Lazy.java
index 112a503..22f948c 100644
--- a/BJC-Utils2/src/main/java/bjc/utils/data/Lazy.java
+++ b/BJC-Utils2/src/main/java/bjc/utils/data/Lazy.java
@@ -43,7 +43,7 @@ public class Lazy<ContainedType> implements IHolder<ContainedType> {
 	 *            The source of a value to use
 	 */
 	public Lazy(Supplier<ContainedType> supp) {
-		valueSupplier = supp;
+		valueSupplier = new SingleSupplier<>(supp);
 
 		valueMaterialized = false;
 	}
diff --git a/BJC-Utils2/src/main/java/bjc/utils/data/LazyPair.java b/BJC-Utils2/src/main/java/bjc/utils/data/LazyPair.java
index e0b39cc..490c4fc 100644
--- a/BJC-Utils2/src/main/java/bjc/utils/data/LazyPair.java
+++ b/BJC-Utils2/src/main/java/bjc/utils/data/LazyPair.java
@@ -29,7 +29,7 @@ public class LazyPair<LeftType, RightType>
 	private boolean				rightMaterialized;
 
 	/**
-	 * Create a new lazy pair, using the set value s
+	 * Create a new lazy pair, using the set values
 	 * 
 	 * @param leftVal
 	 *            The value for the left side of the pair
@@ -54,8 +54,8 @@ public class LazyPair<LeftType, RightType>
 	 */
 	public LazyPair(Supplier<LeftType> leftSupp,
 			Supplier<RightType> rightSupp) {
-		leftSupplier = leftSupp;
-		rightSupplier = rightSupp;
+		leftSupplier = new SingleSupplier<>(leftSupp);
+		rightSupplier = new SingleSupplier<>(rightSupp);
 
 		leftMaterialized = false;
 		rightMaterialized = false;
diff --git a/BJC-Utils2/src/main/java/bjc/utils/data/SingleSupplier.java b/BJC-Utils2/src/main/java/bjc/utils/data/SingleSupplier.java
new file mode 100644
index 0000000..016f492
--- /dev/null
+++ b/BJC-Utils2/src/main/java/bjc/utils/data/SingleSupplier.java
@@ -0,0 +1,34 @@
+package bjc.utils.data;
+
+import java.util.function.Supplier;
+
+public class SingleSupplier<T> implements Supplier<T> {
+	private Supplier<T>	source;
+
+	private boolean		gotten;
+
+	private long		id;
+
+	private static long	nextID	= 0;
+
+	public SingleSupplier(Supplier<T> supp) {
+		source = supp;
+
+		gotten = false;
+
+		id = nextID++;
+	}
+
+	@Override
+	public T get() {
+		if (gotten == true) {
+			throw new IllegalStateException(
+					"Attempted to get value more than once"
+							+ " from single supplier #" + id);
+		}
+
+		gotten = true;
+
+		return source.get();
+	}
+}