Removed use of Guava's Cache because Bukkit uses an ancient version of Guava.

src/main/java/com/sk89q/worldedit/util/annotation/RequiresNewerGuava.java

@@ -0,0 +1,33 @@
+/*
+ * WorldEdit, a Minecraft world manipulation toolkit
+ * Copyright (C) sk89q <http://www.sk89q.com>
+ * Copyright (C) WorldEdit team and contributors
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.sk89q.worldedit.util.annotation;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+
+/**
+ * Marks features that should be replaced with Google Guava but cannot
+ * yet because Bukkit uses such an old version of Guava.
+ */
+@Retention(RetentionPolicy.SOURCE)
+@Documented
+public @interface RequiresNewerGuava {
+}

src/main/java/com/sk89q/worldedit/util/eventbus/EventBus.java

@@ -20,16 +20,14 @@
 package com.sk89q.worldedit.util.eventbus;
 
 import com.google.common.base.Supplier;
-import com.google.common.base.Throwables;
+import com.google.common.collect.Multimap;
-import com.google.common.cache.Cache;
+import com.google.common.collect.Multimaps;
-import com.google.common.cache.CacheBuilder;
+import com.google.common.collect.SetMultimap;
-import com.google.common.cache.CacheLoader;
-import com.google.common.collect.*;
 import com.google.common.eventbus.DeadEvent;
+import com.sk89q.worldedit.util.annotation.RequiresNewerGuava;
 
 import java.lang.reflect.InvocationTargetException;
 import java.util.*;
-import java.util.concurrent.ExecutionException;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 
@@ -66,35 +64,8 @@ public class EventBus {
      */
     private final SubscriberFindingStrategy finder = new AnnotatedSubscriberFinder();
 
-    /**
+    @RequiresNewerGuava
-     * A thread-safe cache for flattenHierarchy(). The Class class is immutable.
+    private HierarchyCache flattenHierarchyCache = new HierarchyCache();
-     */
-    private Cache<Class<?>, Set<Class<?>>> flattenHierarchyCache =
-            CacheBuilder.newBuilder()
-                    .weakKeys()
-                    .build(new CacheLoader<Class<?>, Set<Class<?>>>() {
-                        @Override
-                        public Set<Class<?>> load(Class<?> concreteClass) throws Exception {
-                            List<Class<?>> parents = Lists.newLinkedList();
-                            Set<Class<?>> classes = Sets.newHashSet();
-
-                            parents.add(concreteClass);
-
-                            while (!parents.isEmpty()) {
-                                Class<?> clazz = parents.remove(0);
-                                classes.add(clazz);
-
-                                Class<?> parent = clazz.getSuperclass();
-                                if (parent != null) {
-                                    parents.add(parent);
-                                }
-
-                                Collections.addAll(parents, clazz.getInterfaces());
-                            }
-
-                            return classes;
-                        }
-                    });
 
     /**
      * Registers the given handler for the given class to receive events.
@@ -251,11 +222,7 @@ public class EventBus {
      * @return {@code clazz}'s complete type hierarchy, flattened and uniqued.
      */
     Set<Class<?>> flattenHierarchy(Class<?> concreteClass) {
-        try {
         return flattenHierarchyCache.get(concreteClass);
-        } catch (ExecutionException e) {
-            throw Throwables.propagate(e.getCause());
-        }
     }
 
 }

src/main/java/com/sk89q/worldedit/util/eventbus/HierarchyCache.java

@@ -0,0 +1,69 @@
+/*
+ * WorldEdit, a Minecraft world manipulation toolkit
+ * Copyright (C) sk89q <http://www.sk89q.com>
+ * Copyright (C) WorldEdit team and contributors
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.sk89q.worldedit.util.eventbus;
+
+import com.google.common.collect.Lists;
+import com.google.common.collect.Sets;
+import com.sk89q.worldedit.util.annotation.RequiresNewerGuava;
+
+import java.util.*;
+
+/**
+ * Holds a cache of class hierarcy.
+ * </p>
+ * This exists because Bukkit has an ancient version of Guava and the cache
+ * library in Guava has since changed.
+ */
+@RequiresNewerGuava
+class HierarchyCache {
+
+    private final Map<Class<?>, Set<Class<?>>> cache = new WeakHashMap<Class<?>, Set<Class<?>>>();
+
+    public Set<Class<?>> get(Class<?> concreteClass) {
+        Set<Class<?>> ret = cache.get(concreteClass);
+        if (ret == null) {
+            ret = build(concreteClass);
+            cache.put(concreteClass, ret);
+        }
+        return ret;
+    }
+
+    protected Set<Class<?>> build(Class<?> concreteClass) {
+        List<Class<?>> parents = Lists.newLinkedList();
+        Set<Class<?>> classes = Sets.newHashSet();
+
+        parents.add(concreteClass);
+
+        while (!parents.isEmpty()) {
+            Class<?> clazz = parents.remove(0);
+            classes.add(clazz);
+
+            Class<?> parent = clazz.getSuperclass();
+            if (parent != null) {
+                parents.add(parent);
+            }
+
+            Collections.addAll(parents, clazz.getInterfaces());
+        }
+
+        return classes;
+    }
+
+}