1 files changed, 75 insertions, 0 deletions
diff --git a/BJC-Utils2/src/main/java/bjc/utils/graph/GenHolder.java b/BJC-Utils2/src/main/java/bjc/utils/graph/GenHolder.java
new file mode 100644
index 0000000..df363fa
--- /dev/null
+++ b/BJC-Utils2/src/main/java/bjc/utils/graph/GenHolder.java
@@ -0,0 +1,75 @@
+package bjc.utils.graph;
+
+import java.util.function.Function;
+
+/**
+ * Holds a single value of a specific type. This is used for indirect
+ * references to data, and more specifically for accessing non-final
+ * variables from a lambda. AKA the identity monad
+ * 
+ * @author ben
+ *
+ * @param <T>
+ *            The type of the data being held
+ */
+public class GenHolder<T> {
+	/**
+	 * The state this holder is responsible for.
+	 */
+	public T held;
+
+	/**
+	 * Creates a new empty holder, with its state set to null
+	 */
+	public GenHolder() {
+		held = null;
+	}
+
+	/**
+	 * Creates a new holder, with its state initialized to the provided
+	 * value
+	 * 
+	 * @param held
+	 *            The state to initialize this holder to.
+	 */
+	public GenHolder(T hld) {
+		held = hld;
+	}
+
+	/**
+	 * Apply the given transformation to the held value. Returns the holder
+	 * for allowing chaining of transforms
+	 * 
+	 * @param f
+	 *            The transform to apply to the value
+	 * @return The holder
+	 */
+	public GenHolder<T> transform(Function<T, T> f) {
+		held = f.apply(held);
+
+		return this;
+	}
+
+	/**
+	 * Return the result of applying the given transformation to the held
+	 * value Doesn't change the held value
+	 * 
+	 * @param f
+	 *            The transformation to apply
+	 * @return A holder with the transformed value
+	 */
+	public <NewT> GenHolder<NewT> map(Function<T, NewT> f) {
+		return new GenHolder<NewT>(f.apply(held));
+	}
+
+	/**
+	 * Returns a raw mapped value, not contained in a GenHolder
+	 * 
+	 * @param f
+	 *            The function to use for mapping the value
+	 * @return The mapped value outside of a GenHolder
+	 */
+	public <E> E unwrap(Function<T, E> f) {
+		return f.apply(held);
+	}
+}