CatServer/patches/net/minecraft/util/ClassInheritanceMultiMap.java.patch

--- ../src-base/minecraft/net/minecraft/util/ClassInheritanceMultiMap.java
+++ ../src-work/minecraft/net/minecraft/util/ClassInheritanceMultiMap.java
@@ -13,7 +13,8 @@
 
 public class ClassInheritanceMultiMap<T> extends AbstractSet<T>
 {
-    private static final Set < Class<? >> ALL_KNOWN = Sets. < Class<? >> newHashSet();
+    // Forge: Use concurrent collection to allow creating chunks from multiple threads safely
+    private static final Set < Class<? >> ALL_KNOWN = Collections.newSetFromMap(new java.util.concurrent.ConcurrentHashMap<Class<?>, Boolean>());
     private final Map < Class<?>, List<T >> map = Maps. < Class<?>, List<T >> newHashMap();
     private final Set < Class<? >> knownKeys = Sets. < Class<? >> newIdentityHashSet();
     private final Class<T> baseClass;
@@ -122,6 +123,17 @@
         {
             public Iterator<S> iterator()
             {
+                // CatServer start - Optimization from Foamfix
+                Class c = ClassInheritanceMultiMap.this.initializeClassLookup(clazz);
+                List<T> list = ClassInheritanceMultiMap.this.map.get(c);
+                if (list == null) {
+                    return Collections.emptyIterator();
+                } else {
+                    Iterator<T> iterator = list.iterator();
+                    return clazz == c ? (Iterator<S>) iterator : Iterators.filter(iterator, clazz);
+                }
+                // CatServer end
+                /*
                 List<T> list = (List)ClassInheritanceMultiMap.this.map.get(ClassInheritanceMultiMap.this.initializeClassLookup(clazz));
 
                 if (list == null)
@@ -133,6 +145,7 @@
                     Iterator<T> iterator = list.iterator();
                     return Iterators.filter(iterator, clazz);
                 }
+                */
             }
         };
     }