Ensure supplier don't materialize more than once

1 files changed, 34 insertions, 0 deletions

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();
+	}
+}