7 files changed, 44 insertions, 59 deletions
diff --git a/src/main/java/bjc/esodata/PushdownMap.java b/src/main/java/bjc/esodata/PushdownMap.java
index a30161c..410eb53 100644
--- a/src/main/java/bjc/esodata/PushdownMap.java
+++ b/src/main/java/bjc/esodata/PushdownMap.java
@@ -1,7 +1,9 @@
 package bjc.esodata;
 
+import java.util.*;
 import java.util.function.*;
 
+import bjc.data.*;
 import bjc.funcdata.*;
 
 /**
@@ -48,8 +50,8 @@ public class PushdownMap<KeyType, ValueType> implements IMap<KeyType, ValueType>
 	}
 
 	@Override
-	public ValueType get(final KeyType key) {
-		return backing.get(key).top();
+	public Optional<ValueType> get(final KeyType key) {
+		return backing.get(key).map((stack) -> stack.top());
 	}
 
 	@Override
@@ -67,7 +69,7 @@ public class PushdownMap<KeyType, ValueType> implements IMap<KeyType, ValueType>
 		if (isFrozen) throw new ObjectFrozen("Can't insert key " + key + " into frozen map");
 		
 		if (backing.containsKey(key)) {
-			final Stack<ValueType> stk = backing.get(key);
+			final Stack<ValueType> stk = backing.get(key).get();
 
 			final ValueType vl = stk.top();
 
@@ -86,12 +88,18 @@ public class PushdownMap<KeyType, ValueType> implements IMap<KeyType, ValueType>
 	@Override
 	public ValueType remove(final KeyType key) {
 		if (isFrozen) throw new ObjectFrozen("Can't remove key " + key + " from frozen map");
-	
-		final Stack<ValueType> stk = backing.get(key);
-
-		if (stk.size() > 1) return stk.pop();
 
-		return backing.remove(key).top();
+		IHolder<ValueType> result = IHolder.of(null);
+		
+		backing.get(key).ifPresent((stk) -> {
+			if (stk.size() > 1) {
+				result.replace(stk.pop());
+			} else {
+				result.replace(backing.remove(key).top());
+			}
+		});
+
+		return result.getValue();
 	}
 
 	@Override
diff --git a/src/main/java/bjc/esodata/SimpleDirectory.java b/src/main/java/bjc/esodata/SimpleDirectory.java
index 36f5f5a..ddc65b4 100644
--- a/src/main/java/bjc/esodata/SimpleDirectory.java
+++ b/src/main/java/bjc/esodata/SimpleDirectory.java
@@ -30,7 +30,7 @@ public class SimpleDirectory<K, V> implements Directory<K, V> {
 
 	@Override
 	public Directory<K, V> getSubdirectory(final K key) {
-		return children.get(key);
+		return children.get(key).orElse(null);
 	}
 
 	@Override
@@ -50,7 +50,7 @@ public class SimpleDirectory<K, V> implements Directory<K, V> {
 
 	@Override
 	public V getKey(final K key) {
-		return data.get(key);
+		return data.get(key).orElse(null);
 	}
 
 	@Override
diff --git a/src/main/java/bjc/esodata/UnifiedDirectory.java b/src/main/java/bjc/esodata/UnifiedDirectory.java
index dcbac89..abf9a4c 100644
--- a/src/main/java/bjc/esodata/UnifiedDirectory.java
+++ b/src/main/java/bjc/esodata/UnifiedDirectory.java
@@ -30,7 +30,7 @@ public class UnifiedDirectory<K, V> implements Directory<K, V> {
 
 	@Override
 	public Directory<K, V> getSubdirectory(final K key) {
-		return children.get(key);
+		return children.get(key).orElse(null);
 	}
 
 	@Override
@@ -56,7 +56,7 @@ public class UnifiedDirectory<K, V> implements Directory<K, V> {
 
 	@Override
 	public V getKey(final K key) {
-		return data.get(key);
+		return data.get(key).orElse(null);
 	}
 
 	@Override
diff --git a/src/main/java/bjc/funcdata/ExtendedMap.java b/src/main/java/bjc/funcdata/ExtendedMap.java
index 059181f..9638cdc 100644
--- a/src/main/java/bjc/funcdata/ExtendedMap.java
+++ b/src/main/java/bjc/funcdata/ExtendedMap.java
@@ -60,7 +60,7 @@ class ExtendedMap<KeyType, ValueType> implements IMap<KeyType, ValueType> {
 	}
 
 	@Override
-	public ValueType get(final KeyType key) {
+	public Optional<ValueType> get(final KeyType key) {
 		if (store.containsKey(key)) return store.get(key);
 		else                        return delegate.get(key);
 	}
diff --git a/src/main/java/bjc/funcdata/FunctionalMap.java b/src/main/java/bjc/funcdata/FunctionalMap.java
index 9836c98..3ab2598 100644
--- a/src/main/java/bjc/funcdata/FunctionalMap.java
+++ b/src/main/java/bjc/funcdata/FunctionalMap.java
@@ -73,16 +73,14 @@ public class FunctionalMap<KeyType, ValueType> implements IMap<KeyType, ValueTyp
 	}
 
 	@Override
-	public ValueType get(final KeyType key) {
+	public Optional<ValueType> get(final KeyType key) {
 		if (key == null) throw new NullPointerException("Key must not be null");
 
-		if (!wrappedMap.containsKey(key)) {
-			final String msg = String.format("Key %s is not present in the map", key);
-
-			throw new IllegalArgumentException(msg);
+		if (wrappedMap.containsKey(key)) {
+			return Optional.of(wrappedMap.get(key));
+		} else {
+			return Optional.empty();
 		}
-
-		return wrappedMap.get(key);
 	}
 
 	@Override
@@ -138,8 +136,8 @@ public class FunctionalMap<KeyType, ValueType> implements IMap<KeyType, ValueTyp
 		if (wrappedMap == null) {
 			if (other.wrappedMap != null) return false;
 		} else if (!wrappedMap.equals(other.wrappedMap)) {
-      return false;
-    }
+			return false;
+		}
 		
 		return true;
 	}
diff --git a/src/main/java/bjc/funcdata/IMap.java b/src/main/java/bjc/funcdata/IMap.java
index 4eaa9c0..ca9ef11 100644
--- a/src/main/java/bjc/funcdata/IMap.java
+++ b/src/main/java/bjc/funcdata/IMap.java
@@ -1,5 +1,6 @@
 package bjc.funcdata;
 
+import java.util.*;
 import java.util.function.*;
 
 /**
@@ -60,31 +61,7 @@ public interface IMap<KeyType, ValueType> extends IFreezable {
 	 *
 	 * @return The value of the key.
 	 */
-	ValueType get(KeyType key);
-
-	/**
-	 * Get a value from the map, and return a default value if the key doesn't
-	 * exist.
-	 *
-	 * @param key
-	 *                     The key to attempt to retrieve.
-	 *
-	 * @param defaultValue
-	 *                     The value to return if the key doesn't exist.
-	 *
-	 * @return The value associated with the key, or the default value if the key
-	 *         doesn't exist.
-	 */
-	default ValueType getOrDefault(final KeyType key, final ValueType defaultValue) {
-		try {
-			return get(key);
-		} catch (final IllegalArgumentException iaex) {
-			/*
-			 * We don't care about this, because it indicates a key is missing.
-			 */
-			return defaultValue;
-		}
-	}
+	Optional<ValueType> get(KeyType key);
 
 	/**
 	 * Add an entry to the map.
@@ -150,7 +127,7 @@ public interface IMap<KeyType, ValueType> extends IFreezable {
 		final IList<ValueType> returns = new FunctionalList<>();
 
 		for (final KeyType key : keyList()) {
-			returns.add(get(key));
+			returns.add(get(key).orElse(null));
 		}
 
 		return returns;
@@ -191,17 +168,18 @@ public interface IMap<KeyType, ValueType> extends IFreezable {
 	   return extend(new FunctionalMap<>());
 	};
 
+	
 	/**
-   * Extends this map, creating a new map that will delegate queries to this map,
-   * but store any added values in the provided map.
-   *
-   * @param backer The map to store added values in.
-   * 
-   * @return An extended map.
-   */
+	 * Extend this map, creating a new map that will delegate queries to 
+	 * the current map but store any added values in the provided map.
+	 * 
+	 * @param backer The map to store values in.
+	 * 
+	 * @return An extended map, with the specified backing map.
+	 */
 	default IMap<KeyType, ValueType> extend(IMap<KeyType, ValueType> backer) {
-    return new ExtendedMap<>(this, backer);
- };
+		return new ExtendedMap<>(this, backer);
+	};
 	
 	/**
 	 * Static method to create a basic instance of IMap.
diff --git a/src/main/java/bjc/funcdata/TransformedValueMap.java b/src/main/java/bjc/funcdata/TransformedValueMap.java
index cf4a9d8..1e0ef51 100644
--- a/src/main/java/bjc/funcdata/TransformedValueMap.java
+++ b/src/main/java/bjc/funcdata/TransformedValueMap.java
@@ -1,5 +1,6 @@
 package bjc.funcdata;
 
+import java.util.*;
 import java.util.function.*;
 
 /**
@@ -62,8 +63,8 @@ final class TransformedValueMap<OldKey, OldValue, NewValue>
 	}
 
 	@Override
-	public NewValue get(final OldKey key) {
-		return transformer.apply(backing.get(key));
+	public Optional<NewValue> get(final OldKey key) {
+		return backing.get(key).map(transformer);
 	}
 
 	@Override