switch from harcoded string to enum and remove complexity in some actions

pom.xml

@@ -20,6 +20,12 @@
             <version>1.2.1</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.jetbrains</groupId>
+            <artifactId>annotations</artifactId>
+            <version>23.0.0</version>
+            <scope>compile</scope>
+        </dependency>
     </dependencies>
 
     <properties>

src/main/java/com/github/dtschust/zork/Zork.java

@@ -11,11 +11,14 @@ import com.github.dtschust.zork.repl.ActionDispatcher;
 import com.github.dtschust.zork.types.ZorkContainer;
 import com.github.dtschust.zork.types.ZorkObject;
 
+import java.util.Iterator;
 import java.util.Scanner;
 
+import static com.github.dtschust.zork.Zork.Type.*;
 
 /* And away we go*/
 public class Zork {
+    public enum Type {ROOM, ITEM, CONTAINER, CREATURE}
     public String userInput;
 
     public ZorkGame game;
@@ -85,7 +88,7 @@ public class Zork {
     private boolean doTriggersContainersInRoom() {
         boolean skip = false;
         for (String key : game.getCurrentRoom().container) {
-            skip = skip || doZorkTriggers(game.get("container", key));
+            skip = skip || doZorkTriggers(game.get(CONTAINER, key));
         }
         return skip;
     }
@@ -93,9 +96,9 @@ public class Zork {
     private boolean doTriggersItemsInContainersInRoom() {
         boolean skip = false;
         for (String key : game.getCurrentRoom().container) {
-            ZorkContainer tempContainer = (ZorkContainer) game.get("container", key);
+            ZorkContainer tempContainer = (ZorkContainer) game.get(CONTAINER, key);
             for (String key2 : tempContainer.item) {
-                skip = skip || doZorkTriggers(game.get("item", key2));
+                skip = skip || doZorkTriggers(game.get(ITEM, key2));
             }
         }
         return skip;
@@ -104,7 +107,7 @@ public class Zork {
     private boolean doTriggersItemsInRoom() {
         boolean skip = false;
         for (String key : game.getCurrentRoom().item) {
-            skip = skip || doZorkTriggers(game.get("item", key));
+            skip = skip || doZorkTriggers(game.get(ITEM, key));
         }
         return skip;
     }
@@ -112,7 +115,7 @@ public class Zork {
     private boolean doTriggersItemsInInventory() {
         boolean skip = false;
         for (String key : game.inventory) {
-            skip = skip || doZorkTriggers(game.get("item", key));
+            skip = skip || doZorkTriggers(game.get(ITEM, key));
         }
         return skip;
     }
@@ -120,7 +123,7 @@ public class Zork {
     private boolean doTriggersCreaturesInRoom() {
         boolean skip = false;
         for (String key : game.getCurrentRoom().creature) {
-            skip = skip || doZorkTriggers(game.get("creature", key));
+            skip = skip || doZorkTriggers(game.get(CREATURE, key));
         }
         return skip;
     }
@@ -132,8 +135,9 @@ public class Zork {
 
     private boolean doZorkTriggers(ZorkObject zorkObject) {
         boolean skip = false;
-        for (int x = zorkObject.trigger.size() - 1; x >= 0; x--) {
+        Iterator<ZorkTrigger> iterator = zorkObject.trigger.iterator();
-            ZorkTrigger tempTrigger = zorkObject.trigger.get(x);
+        while (iterator.hasNext()) {
+            ZorkTrigger tempTrigger = iterator.next();
             if (tempTrigger.evaluate(this)) {
                 for (String print : tempTrigger.print) {
                     System.out.println(print);
@@ -144,7 +148,7 @@ public class Zork {
                 }
                 skip = skip || tempTrigger.hasCommand();
                 if (tempTrigger.type.equals("single")) {
-                    zorkObject.trigger.remove(x);
+                    iterator.remove();
                 }
             }
         }

src/main/java/com/github/dtschust/zork/ZorkConditionHas.java

@@ -4,6 +4,8 @@ import com.github.dtschust.zork.parser.ZorkGame;
 import com.github.dtschust.zork.types.ZorkContainer;
 import com.github.dtschust.zork.types.ZorkRoom;
 
+import static com.github.dtschust.zork.Zork.Type.*;
+
 
 /* Has conditions*/
 public class ZorkConditionHas extends ZorkCondition {
@@ -23,13 +25,13 @@ public class ZorkConditionHas extends ZorkCondition {
             return evaluateCondition(game.inventory.contains(object));
         } else {
             /* is it a room?*/
-            ZorkRoom roomObject = (ZorkRoom) game.get("room", owner);
+            ZorkRoom roomObject = (ZorkRoom) game.get(ROOM, owner);
             if (roomObject != null) {
                 return evaluateCondition(roomObject.item.contains(object));
             }
             /* is it a container?*/
             else {
-                ZorkContainer containerObject = (ZorkContainer) game.get("container", owner);
+                ZorkContainer containerObject = (ZorkContainer) game.get(CONTAINER, owner);
                 if (containerObject != null) {
                     return evaluateCondition(containerObject.containsItem(object));
                 }

src/main/java/com/github/dtschust/zork/ZorkConditionStatus.java

@@ -14,7 +14,7 @@ public class ZorkConditionStatus extends ZorkCondition {
 
     @Override
     public boolean evaluate(ZorkGame game) {
-        ZorkObject tested = game.getListThroughLookup(object).get(object);
+        ZorkObject tested = game.getListThroughLookup(ZorkObject.class, object).get(object);
         return tested != null && tested.isStatusEqualTo(status);
     }
 }

src/main/java/com/github/dtschust/zork/parser/ZorkGame.java

@@ -1,5 +1,6 @@
 package com.github.dtschust.zork.parser;
 
+import com.github.dtschust.zork.Zork.Type;
 import com.github.dtschust.zork.types.*;
 
 import java.util.HashMap;
@@ -15,7 +16,7 @@ public class ZorkGame {
     protected ZorkMap<ZorkItem> items = new ZorkMap<>();
     protected ZorkMap<ZorkContainer> containers = new ZorkMap<>();
     protected ZorkMap<ZorkCreature> creatures = new ZorkMap<>();
-    protected HashMap<String, String> objectLookup = new HashMap<>();
+    protected HashMap<String, Type> objectLookup = new HashMap<>();
 
     public ZorkRoom getCurrentRoom() {
         return rooms.get(currentRoom);
@@ -38,58 +39,59 @@ public class ZorkGame {
         running = false;
     }
 
-    public String getTypeFromLookup(String object) {
+    public Type getTypeFromLookup(String object) {
         return objectLookup.get(object);
     }
 
-    public void addObjectThroughLookup(String name, ZorkObject object) {
+    public void addObjectThroughLookup(Type type, ZorkObject object) {
-        putInMapGivenType(name, object);
+        putInMapGivenType(type, object);
-        objectLookup.put(object.name, name);
+        objectLookup.put(object.name, type);
     }
 
-    public ZorkMap<? extends ZorkObject> getListThroughLookup(String name) {
+    public <T extends ZorkObject> ZorkMap<T> getListThroughLookup(Class<T> cast, String name) {
-        return getMapFromType(objectLookup.get(name));
+        return values(cast, objectLookup.get(name));
     }
 
-    public ZorkObject get(String type, String key) {
+    public <T extends ZorkObject> ZorkMap<T> values(Class<T> cast, Type type) {
+        return (ZorkMap<T>) getMapFromType(type);
+    }
+
+    public ZorkObject get(Type type, String key) {
         return getMapFromType(type).get(key);
     }
 
-    public void put(String type, ZorkObject object) {
+    public void put(Type type, ZorkObject object) {
         putInMapGivenType(type, object);
     }
 
-    public Iterable<? extends ZorkObject> values(String type) {
-        return getMapFromType(type).values();
-    }
 
-    private ZorkMap<? extends ZorkObject> getMapFromType(String type) {
+    private ZorkMap<? extends ZorkObject> getMapFromType(Type type) {
         switch (type) {
-            case "room":
+            case ROOM:
                 return rooms;
-            case "container":
+            case CONTAINER:
                 return containers;
-            case "creature":
+            case CREATURE:
                 return creatures;
-            case "item":
+            case ITEM:
                 return items;
             default:
                 throw new IllegalStateException("Unexpected value: " + type);
         }
     }
 
-    private void putInMapGivenType(String type, ZorkObject object) {
+    private void putInMapGivenType(Type type, ZorkObject object) {
         switch (type) {
-            case "room":
+            case ROOM:
                 rooms.put((ZorkRoom) object);
                 break;
-            case "container":
+            case CONTAINER:
                 containers.put((ZorkContainer) object);
                 break;
-            case "creature":
+            case CREATURE:
                 creatures.put((ZorkCreature) object);
                 break;
-            case "item":
+            case ITEM:
                 items.put((ZorkItem) object);
                 break;
             default:

src/main/java/com/github/dtschust/zork/parser/ZorkReader.java

@@ -19,6 +19,9 @@ import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
 import java.util.stream.Collectors;
+import java.nio.channels.NonReadableChannelException;
+
+import static com.github.dtschust.zork.Zork.Type.*;
 
 public class ZorkReader {
 
@@ -72,14 +75,14 @@ public class ZorkReader {
         tempCreature.updateStatus(DOMUtils.getInnerTextByTagName(element, "status", ""));
 
         /* Put each creature in the creatures hashmap, the generic object hashmap, and the objectlookup hashmap*/
-        data.addObjectThroughLookup("creature", tempCreature);
+        data.addObjectThroughLookup(CREATURE, tempCreature);
     }
 
     private static void addContainer(ZorkGame data, Element element) {
         final ZorkContainer tempCont = Parsers.container.parse(element);
 
         /* Put each container in the containers hashmap, the generic object hashmap, and the objectlookup hashmap*/
-        data.addObjectThroughLookup("container", tempCont);
+        data.addObjectThroughLookup(CONTAINER, tempCont);
     }
 
     private static void addItem(ZorkGame data, Element element) {
@@ -111,7 +114,7 @@ public class ZorkReader {
         tempItem.trigger.addAll(triggers);
 
         /* Put each item in the items hashmap, the generic objects hashmap, and store its type in object lookup */
-        data.addObjectThroughLookup("item", tempItem);
+        data.addObjectThroughLookup(ITEM, tempItem);
         tempItem.updateStatus(DOMUtils.getInnerTextByTagName(element, "status", ""));
     }
 
@@ -152,7 +155,7 @@ public class ZorkReader {
             tempRoom.border.put(borderDirection, borderName);
         }
         /*Add this room to the rooms hashmap, put it in the generic objects hashmap, and store it's type in the objectlookup hashmap*/
-        data.addObjectThroughLookup("room", tempRoom);
+        data.addObjectThroughLookup(ROOM, tempRoom);
     }
 
     public ZorkGame build() {
@@ -161,7 +164,7 @@ public class ZorkReader {
         File file = new File(filename);
         if (!file.canRead()) {
             System.out.println("Error opening file.  Exiting...");
-            throw new RuntimeException();
+            throw new NonReadableChannelException();
         }
 
         try {
@@ -198,6 +201,8 @@ public class ZorkReader {
                         case "creature":
                             addCreature(data, element);
                             break;
+                        default:
+                            throw new IllegalStateException("Unexpected value: " + tagType);
                     }
 
                 }
@@ -206,7 +211,6 @@ public class ZorkReader {
             e.printStackTrace();
             System.out.println("Invalid XML file, exiting");
             System.exit(-1);
-            //e.printStackTrace();
         }
 
         return data;

src/main/java/com/github/dtschust/zork/repl/Action.java

@@ -4,16 +4,16 @@ import com.github.dtschust.zork.parser.ZorkGame;
 
 import java.util.List;
 
-public abstract class Action {
+public interface Action {
-    public abstract boolean matchesInput(final List<String> arguments);
+    boolean matchesInput(final List<String> arguments);
 
-    public int getMinimumArgCount() {
+    default int getMinimumArgCount() {
         return 1;
     }
 
-    public int getMaximumArgCount() {
+    default int getMaximumArgCount() {
         return Integer.MAX_VALUE;
     }
 
-    public abstract void run(final ZorkGame game, final List<String> arguments);
+    void run(final ZorkGame game, final List<String> arguments);
 }

src/main/java/com/github/dtschust/zork/repl/actions/AddAction.java

@@ -1,16 +1,18 @@
 package com.github.dtschust.zork.repl.actions;
 
 import com.github.dtschust.zork.parser.ZorkGame;
+import com.github.dtschust.zork.Zork.Type;
 import com.github.dtschust.zork.repl.Action;
-import com.github.dtschust.zork.types.ZorkContainer;
+import com.github.dtschust.zork.types.HasSetOfCollectable;
-import com.github.dtschust.zork.types.ZorkRoom;
+import com.github.dtschust.zork.types.ZorkObject;
 
 import java.util.List;
 
+
 /**
  * Add: figure out what type the destination is, then what type the object is.  Then add object to destination if it makes sense
  */
-public class AddAction extends Action {
+public class AddAction implements Action {
     @Override
     public boolean matchesInput(List<String> arguments) {
         return arguments.get(0).equals("Add");
@@ -26,33 +28,13 @@ public class AddAction extends Action {
         final String object = arguments.get(1);
         final String destination = arguments.get(3);
 
-        final String objectType = game.getTypeFromLookup(object);
+        try {
-        final String destinationType = game.getTypeFromLookup(destination);
+            Type destType = game.getTypeFromLookup(destination);
-        if (destinationType.equals("room")) {
+            Type objType = game.getTypeFromLookup(object);
-            ZorkRoom tempRoom = (ZorkRoom) game.get("room", destination);
+            ZorkObject tempObject = game.get(destType, destination);
-            switch (objectType) {
+            ((HasSetOfCollectable) tempObject).getSetFromType(objType).add(object);
-                case "item":
+            game.put(destType, tempObject);
-                    tempRoom.item.add(object);
+        } catch (Exception e) {
-                    break;
-                case "creature":
-                    tempRoom.creature.add(object);
-                    break;
-                case "container":
-                    tempRoom.container.add(object);
-                    break;
-                default:
-                    System.out.println("Error");
-                    break;
-            }
-            game.put("room", tempRoom);
-        } else if (destinationType.equals("container")) {
-            final ZorkContainer tempContainer = (ZorkContainer) game.get("container", destination);
-            if (objectType.equals("item"))
-                tempContainer.item.add(object);
-            else
-                System.out.println("Error");
-            game.put("container", tempContainer);
-        } else {
             System.out.println("Error");
         }
     }

src/main/java/com/github/dtschust/zork/repl/actions/AttackAction.java

@@ -6,10 +6,12 @@ import com.github.dtschust.zork.types.ZorkCreature;
 
 import java.util.List;
 
+import static com.github.dtschust.zork.Zork.Type.CREATURE;
+
 /**
  * Attempt an attack, do you feel lucky?
  */
-public class AttackAction extends Action {
+public class AttackAction implements Action {
     @Override
     public boolean matchesInput(List<String> arguments) {
         return arguments.get(0).equals("attack");
@@ -26,15 +28,13 @@ public class AttackAction extends Action {
         final String weapon = arguments.get(3);
 
         if (game.getCurrentRoom().creature.contains(tempString)) {
-            ZorkCreature tempCreature = (ZorkCreature) game.get("creature", tempString);
+            ZorkCreature tempCreature = (ZorkCreature) game.get(CREATURE, tempString);
-            if (tempCreature != null && game.inventory.contains(weapon)) {
+            if (tempCreature != null && game.inventory.contains(weapon) && tempCreature.isAttackSuccessful(game, weapon)) {
-                if (tempCreature.isAttackSuccessful(game, weapon)) {
                 System.out.println("You assault the " + tempString + " with the " + weapon + ".");
                 tempCreature.printAndExecuteActions(game);
                 return;
             }
         }
-        }
 
         System.out.println("Error");
     }

src/main/java/com/github/dtschust/zork/repl/actions/DeleteAction.java

@@ -1,16 +1,21 @@
 package com.github.dtschust.zork.repl.actions;
 
+import com.github.dtschust.zork.Zork.Type;
 import com.github.dtschust.zork.parser.ZorkGame;
 import com.github.dtschust.zork.repl.Action;
-import com.github.dtschust.zork.types.ZorkContainer;
+import com.github.dtschust.zork.types.HasSetOfCollectable;
+import com.github.dtschust.zork.types.ZorkObject;
 import com.github.dtschust.zork.types.ZorkRoom;
 
 import java.util.List;
+import java.util.Set;
+
+import static com.github.dtschust.zork.Zork.Type.*;
 
 /**
  * Delete: figure out what object it is and delete it accordingly.  Rooms are especially tricky
  */
-public class DeleteAction extends Action {
+public class DeleteAction implements Action {
     @Override
     public boolean matchesInput(List<String> arguments) {
         return arguments.get(0).equals("Delete");
@@ -25,48 +30,37 @@ public class DeleteAction extends Action {
     public void run(ZorkGame game, List<String> arguments) {
         final String object = arguments.get(1);
 
-        String objectType = game.getTypeFromLookup(object);
+        switch (game.getTypeFromLookup(object)) {
-        switch (objectType) {
+            case ROOM:
-            case "room":
+                for (ZorkRoom tempRoom :game.values(ZorkRoom.class, ROOM)) {
-                for (ZorkRoom tempRoom : (Iterable<ZorkRoom>) game.values("room")) {
                     for (String key : tempRoom.border.keySet()) {
                         if (tempRoom.border.get(key).equals(object)) {
                             tempRoom.border.remove(key);
                         }
                     }
-                    game.put("room", tempRoom);
+                    game.put(ROOM, tempRoom);
                 }
                 break;
-            case "item":
+            case ITEM:
-                for (ZorkRoom tempRoom : (Iterable<ZorkRoom>) game.values("room")) {
+                deleteElementFromSpace(game, ROOM, ITEM, object);
-                    if (tempRoom.item.contains(object)) {
+                deleteElementFromSpace(game, CONTAINER, ITEM, object);
-                        tempRoom.item.remove(object);
-                        game.put("room", tempRoom);
-                    }
-                }
-                for (ZorkContainer tempContainer : (Iterable<ZorkContainer>) game.values("container")) {
-                    if (tempContainer.item.contains(object)) {
-                        tempContainer.item.remove(object);
-                        game.put("container", tempContainer);
-                    }
-                }
                 break;
-            case "container":
+            case CONTAINER:
-                for (ZorkRoom tempRoom : (Iterable<ZorkRoom>) game.values("room")) {
+                deleteElementFromSpace(game, ROOM, CONTAINER, object);
-                    if (tempRoom.container.contains(object)) {
-                        tempRoom.container.remove(object);
-                        game.put("room", tempRoom);
-                    }
-                }
                 break;
-            case "creature":
+            case CREATURE:
-                for (ZorkRoom tempRoom : (Iterable<ZorkRoom>) game.values("room")) {
+                deleteElementFromSpace(game, ROOM, CREATURE, object);
-                    if (tempRoom.creature.contains(object)) {
-                        tempRoom.creature.remove(object);
-                        game.put("room", tempRoom);
-                    }
-                }
                 break;
         }
     }
+
+    private static void deleteElementFromSpace(ZorkGame game, Type space, Type element, String object) {
+        for (ZorkObject tempObject : game.values(ZorkObject.class, space)) {
+            Set<String> set = ((HasSetOfCollectable) tempObject).getSetFromType(element);
+            if (set.contains(object)) {
+                set.remove(object);
+                game.put(space, tempObject);
+            }
+        }
+    }
 }

src/main/java/com/github/dtschust/zork/repl/actions/DropItemAction.java

@@ -6,7 +6,9 @@ import com.github.dtschust.zork.types.ZorkRoom;
 
 import java.util.List;
 
-public class DropItemAction extends Action {
+import static com.github.dtschust.zork.Zork.Type.ROOM;
+
+public class DropItemAction implements Action {
     @Override
     public boolean matchesInput(List<String> arguments) {
         return arguments.get(0).equals("drop");
@@ -24,7 +26,7 @@ public class DropItemAction extends Action {
         if (game.inventory.contains(what)) {
             ZorkRoom tempRoom = game.getCurrentRoom();
             tempRoom.item.add(what);
-            game.put("room", tempRoom);
+            game.put(ROOM, tempRoom);
             game.inventory.remove(what);
             System.out.println(what + " dropped.");
         } else {

src/main/java/com/github/dtschust/zork/repl/actions/GameOverAction.java

@@ -8,7 +8,7 @@ import java.util.List;
 /**
  * The "Game Over" action marks the end of the game.
  */
-public class GameOverAction extends Action {
+public class GameOverAction implements Action {
     @Override
     public boolean matchesInput(List<String> arguments) {
         return arguments.get(0).equals("Game") && arguments.get(1).equals("Over");

src/main/java/com/github/dtschust/zork/repl/actions/InventoryAction.java

@@ -5,7 +5,7 @@ import com.github.dtschust.zork.repl.Action;
 
 import java.util.List;
 
-public class InventoryAction extends Action {
+public class InventoryAction implements Action {
     @Override
     public boolean matchesInput(List<String> arguments) {
         return arguments.get(0).equals("i");

src/main/java/com/github/dtschust/zork/repl/actions/MoveAction.java

@@ -13,7 +13,7 @@ import static java.util.Map.entry;
  * Execute a user action or an action command from some <action> element that is not one of the "Special Commands"
  * Movement
  */
-public class MoveAction extends Action {
+public class MoveAction implements Action {
     private static final Map<String, String> fullDirections = Map.ofEntries(
             entry("n", "north"),
             entry("s", "south"),

src/main/java/com/github/dtschust/zork/repl/actions/OpenAction.java

@@ -6,7 +6,9 @@ import com.github.dtschust.zork.types.ZorkContainer;
 
 import java.util.List;
 
-public class OpenAction extends Action {
+import static com.github.dtschust.zork.Zork.Type.CONTAINER;
+
+public class OpenAction implements Action {
     @Override
     public boolean matchesInput(List<String> arguments) {
         return arguments.get(0).equals("open");
@@ -26,7 +28,7 @@ public class OpenAction extends Action {
         } else {
             ZorkContainer tempContainer;
             if (game.getCurrentRoom().container.contains(what)) {
-                tempContainer = (ZorkContainer) game.get("container", what);
+                tempContainer = (ZorkContainer) game.get(CONTAINER, what);
                 tempContainer.open();
                 if (tempContainer.item.isEmpty()) {
                     System.out.println(what + " is empty");

src/main/java/com/github/dtschust/zork/repl/actions/PutAction.java

@@ -6,7 +6,9 @@ import com.github.dtschust.zork.types.ZorkContainer;
 
 import java.util.List;
 
-public class PutAction extends Action {
+import static com.github.dtschust.zork.Zork.Type.CONTAINER;
+
+public class PutAction implements Action {
     @Override
     public boolean matchesInput(List<String> arguments) {
         return arguments.get(0).equals("put");
@@ -23,7 +25,7 @@ public class PutAction extends Action {
         final String destination = arguments.get(3);
 
         if (game.getCurrentRoom().container.contains(destination)) {
-            ZorkContainer tempContainer = (ZorkContainer) game.get("container", destination);
+            ZorkContainer tempContainer = (ZorkContainer) game.get(CONTAINER, destination);
             if (tempContainer.isOpen() && game.inventory.contains(what)) {
                 tempContainer.item.add(what);
                 game.inventory.remove(what);

src/main/java/com/github/dtschust/zork/repl/actions/ReadAction.java

@@ -6,7 +6,9 @@ import com.github.dtschust.zork.types.ZorkItem;
 
 import java.util.List;
 
-public class ReadAction extends Action {
+import static com.github.dtschust.zork.Zork.Type.ITEM;
+
+public class ReadAction implements Action {
     @Override
     public boolean matchesInput(List<String> arguments) {
         return arguments.get(0).equals("read");
@@ -22,7 +24,7 @@ public class ReadAction extends Action {
         final String what = arguments.get(1);
 
         if (game.inventory.contains(what)) {
-            ZorkItem tempItem = (ZorkItem) game.get("item", what);
+            ZorkItem tempItem = (ZorkItem) game.get(ITEM, what);
             if (tempItem.writing != null && !tempItem.writing.isEmpty()) {
                 System.out.println(tempItem.writing);
             } else {

src/main/java/com/github/dtschust/zork/repl/actions/TakeAction.java

@@ -7,7 +7,9 @@ import com.github.dtschust.zork.types.ZorkRoom;
 
 import java.util.List;
 
-public class TakeAction extends Action {
+import static com.github.dtschust.zork.Zork.Type.*;
+
+public class TakeAction implements Action {
     @Override
     public boolean matchesInput(List<String> arguments) {
         return arguments.get(0).equals("take");
@@ -26,16 +28,16 @@ public class TakeAction extends Action {
             game.inventory.add(tempString);
             ZorkRoom tempRoom = (game.getCurrentRoom());
             tempRoom.item.remove(tempString);
-            game.put("room", tempRoom);
+            game.put(ROOM, tempRoom);
             System.out.println("Item " + tempString + " added to inventory.");
         } else {
             /* Search all containers in the current room for the item! */
             for (String key : game.getCurrentRoom().container) {
-                ZorkContainer tempContainer = (ZorkContainer) game.get("container", key);
+                ZorkContainer tempContainer = (ZorkContainer) game.get(CONTAINER, key);
                 if (tempContainer != null && tempContainer.isOpen() && tempContainer.item.contains(tempString)) {
                     game.inventory.add(tempString);
                     tempContainer.item.remove(tempString);
-                    game.put("container", tempContainer);
+                    game.put(CONTAINER, tempContainer);
                     System.out.println("Item " + tempString + " added to inventory.");
                     return;
                 }

src/main/java/com/github/dtschust/zork/repl/actions/TurnOnAction.java

@@ -6,10 +6,12 @@ import com.github.dtschust.zork.types.ZorkItem;
 
 import java.util.List;
 
+import static com.github.dtschust.zork.Zork.Type.ITEM;
+
 /**
  * Turn on an item
  */
-public class TurnOnAction extends Action {
+public class TurnOnAction implements Action {
     @Override
     public boolean matchesInput(List<String> arguments) {
         return arguments.get(0).equals("turn") && arguments.get(1).equals("on");
@@ -25,7 +27,7 @@ public class TurnOnAction extends Action {
         final String what = arguments.get(2);
 
         if (game.inventory.contains(what)) {
-            ZorkItem tempItem = (ZorkItem) game.get("item", what);
+            ZorkItem tempItem = (ZorkItem) game.get(ITEM, what);
             System.out.println("You activate the " + what + ".");
             if (tempItem != null) {
                 tempItem.printAndExecuteActions(game);

src/main/java/com/github/dtschust/zork/repl/actions/UpdateAction.java

@@ -10,7 +10,7 @@ import java.util.List;
 /**
  * The "Update" command figures out what type of item it is, and then change its status
  */
-public class UpdateAction extends Action {
+public class UpdateAction implements Action {
     @Override
     public boolean matchesInput(List<String> arguments) {
         return arguments.get(0).equals("Update");
@@ -26,7 +26,7 @@ public class UpdateAction extends Action {
         final String object = arguments.get(1);
         final String newStatus = arguments.get(3);
 
-        ZorkMap<ZorkObject> collection = (ZorkMap<ZorkObject>) game.getListThroughLookup(object);
+        ZorkMap<ZorkObject> collection = game.getListThroughLookup(ZorkObject.class, object);
         ZorkObject tempObject = collection.get(object);
         tempObject.updateStatus(newStatus);
         collection.put(tempObject);

src/main/java/com/github/dtschust/zork/types/HasSetOfCollectable.java

@@ -0,0 +1,12 @@
+package com.github.dtschust.zork.types;
+
+import com.github.dtschust.zork.Zork;
+
+import java.util.Set;
+
+public interface HasSetOfCollectable {
+
+    default Set<String> getSetFromType(Zork.Type type) {
+        throw new UnsupportedOperationException();
+    }
+}

src/main/java/com/github/dtschust/zork/types/ZorkContainer.java

@@ -1,11 +1,14 @@
 package com.github.dtschust.zork.types;
 
+import com.github.dtschust.zork.Zork;
 import com.github.dtschust.zork.ZorkTrigger;
 
 import java.util.*;
 
+import static com.github.dtschust.zork.Zork.Type.ITEM;
+
 /* Container*/
-public class ZorkContainer extends ZorkObject {
+public class ZorkContainer extends ZorkObject implements HasSetOfCollectable {
     public final Set<String> item;
     private final List<String> accepts;
     private boolean open;
@@ -46,4 +49,11 @@ public class ZorkContainer extends ZorkObject {
     public void open() {
         open = true;
     }
+
+    @Override
+    public Set<String> getSetFromType(Zork.Type type) {
+        if (type.equals(ITEM))
+            return item;
+        throw new IllegalStateException("Unexpected value: " + type);
+    }
 }

src/main/java/com/github/dtschust/zork/types/ZorkMap.java

@@ -1,11 +1,17 @@
 package com.github.dtschust.zork.types;
 
 import java.util.HashMap;
+import java.util.Iterator;
 
-public class ZorkMap<T extends ZorkObject> extends HashMap<String, T> {
+public class ZorkMap<T extends ZorkObject> extends HashMap<String, T> implements Iterable<T> {
 
     public T put(T object) {
         return put(object.name, object);
     }
+
+    @Override
+    public Iterator<T> iterator() {
+        return this.values().iterator();
+    }
 }
 

src/main/java/com/github/dtschust/zork/types/ZorkObject.java

@@ -36,4 +36,5 @@ public abstract class ZorkObject {
     public boolean isStatusEqualTo(String status) {
         return this.status.equals(status);
     }
+
 }

src/main/java/com/github/dtschust/zork/types/ZorkRoom.java

@@ -1,12 +1,14 @@
 package com.github.dtschust.zork.types;
 
+import com.github.dtschust.zork.Zork;
+
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Map;
 import java.util.Set;
 
 /*  Room*/
-public class ZorkRoom extends ZorkObject {
+public class ZorkRoom extends ZorkObject implements HasSetOfCollectable {
     public final String type;
     public final Map<String, String> border = new HashMap<>();
     public final Set<String> container = new HashSet<>();
@@ -17,4 +19,18 @@ public class ZorkRoom extends ZorkObject {
         super(name, description);
         this.type = type;
     }
+
+    @Override
+    public Set<String> getSetFromType(Zork.Type type) {
+        switch (type) {
+            case CONTAINER:
+                return container;
+            case CREATURE:
+                return creature;
+            case ITEM:
+                return item;
+            default:
+                throw new IllegalStateException("Unexpected value: " + type);
+        }
+    }
 }