Add a helper for casting some common collection types into generic form

fml/src/main/java/cpw/mods/fml/common/functions/CollectionWrapperFactory.java

@@ -0,0 +1,32 @@
+package cpw.mods.fml.common.functions;
+
+import java.util.Collection;
+import java.util.List;
+import com.google.common.collect.Collections2;
+import com.google.common.collect.Lists;
+
+public class CollectionWrapperFactory {
+    /**
+     * Return a read only cast view of the supplied ungeneric collection, based on the element type given
+     * @param coll The collection to cast
+     * @param elementType the supertype contained in the collection
+     * @return a collection asserting that type relationship
+     */
+    public static <T> Collection<T> wrap(@SuppressWarnings("rawtypes") Collection coll, Class<T> elementType)
+    {
+        Collection<?> asGeneric = coll;
+        return Collections2.transform(asGeneric, new TypeCastFunction<T>(elementType));
+    }
+
+    /**
+     * Return a read only cast view of the supplied ungeneric list, based on the element type given
+     * @param list The list to cast
+     * @param elementType the supertype contained in the list
+     * @return a list asserting that type relationship
+     */
+    public static <T> List<T> wrap(@SuppressWarnings("rawtypes") List list, Class<T> elementType)
+    {
+        List<?> asGeneric = list;
+        return Lists.transform(asGeneric, new TypeCastFunction<T>(elementType));
+    }
+}