diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/GenericResourceAllocation.java b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/GenericResourceAllocation.java
index 6d4ac9682..beff50a2e 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/GenericResourceAllocation.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/GenericResourceAllocation.java
@@ -85,27 +85,6 @@ public class GenericResourceAllocation extends
         return result;
     }
 
-    public static Map<Resource, List<GenericResourceAllocation>> byResource(
-            Collection<GenericResourceAllocation> allocations) {
-        Map<Resource, List<GenericResourceAllocation>> result = new HashMap<Resource, List<GenericResourceAllocation>>();
-        for (GenericResourceAllocation resourceAllocation : allocations) {
-            for (Resource resource : resourceAllocation
-                    .getAssociatedResources()) {
-                initializeIfNeeded_(result, resource);
-                result.get(resource).add(resourceAllocation);
-            }
-        }
-        return result;
-    }
-
-    private static void initializeIfNeeded_(
-            Map<Resource, List<GenericResourceAllocation>> result,
-            Resource resource) {
-        if (!result.containsKey(resource)) {
-            result.put(resource, new ArrayList<GenericResourceAllocation>());
-        }
-    }
-
     @OnCopy(Strategy.SHARE_COLLECTION_ELEMENTS)
     private Set<Criterion> criterions = new HashSet<Criterion>();
 
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/ResourceAllocation.java b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/ResourceAllocation.java
index e30d541db..92663b25b 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/ResourceAllocation.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/ResourceAllocation.java
@@ -103,6 +103,21 @@ public abstract class ResourceAllocation<T extends DayAssignment> extends
         return result;
     }
 
+    public static <R extends ResourceAllocation<?>> Map<Resource, List<R>> byResource(
+            Collection<? extends R> allocations) {
+        Map<Resource, List<R>> result = new HashMap<Resource, List<R>>();
+        for (R resourceAllocation : allocations) {
+            for (Resource resource : resourceAllocation
+                    .getAssociatedResources()) {
+                if (!result.containsKey(resource)) {
+                    result.put(resource, new ArrayList<R>());
+                }
+                result.get(resource).add(resourceAllocation);
+            }
+        }
+        return result;
+    }
+
     public static <R extends ResourceAllocation<?>> List<R> sortedByStartDate(
             Collection<R> allocations) {
         List<R> result = new ArrayList<R>(allocations);