Index: trunk/src/org/openstreetmap/josm/data/osm/IPrimitive.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/osm/IPrimitive.java	(revision 13666)
+++ trunk/src/org/openstreetmap/josm/data/osm/IPrimitive.java	(revision 13667)
@@ -364,4 +364,13 @@
 
     /**
+     * Determines if this object is a relation and behaves as a multipolygon.
+     * @return {@code true} if it is a real multipolygon or a boundary relation
+     * @since 13667
+     */
+    default boolean isMultipolygon() {
+        return false;
+    }
+
+    /**
      * true if this object has direction dependent tags (e.g. oneway)
      * @return {@code true} if this object has direction dependent tags
Index: trunk/src/org/openstreetmap/josm/data/osm/IRelation.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/osm/IRelation.java	(revision 13666)
+++ trunk/src/org/openstreetmap/josm/data/osm/IRelation.java	(revision 13667)
@@ -54,3 +54,16 @@
         return formatter.format(this);
     }
+
+    /**
+     * Determines if this relation is a boundary.
+     * @return {@code true} if a boundary relation
+     */
+    default boolean isBoundary() {
+        return "boundary".equals(get("type"));
+    }
+
+    @Override
+    default boolean isMultipolygon() {
+        return "multipolygon".equals(get("type")) || isBoundary();
+    }
 }
Index: trunk/src/org/openstreetmap/josm/data/osm/OsmPrimitive.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/osm/OsmPrimitive.java	(revision 13666)
+++ trunk/src/org/openstreetmap/josm/data/osm/OsmPrimitive.java	(revision 13667)
@@ -1351,13 +1351,4 @@
 
     /**
-     * Determines if this object is a relation and behaves as a multipolygon.
-     * @return {@code true} if it is a real mutlipolygon or a boundary relation
-     * @since 10716
-     */
-    public boolean isMultipolygon() {
-        return false;
-    }
-
-    /**
      * If necessary, extend the bbox to contain this primitive
      * @param box a bbox instance
Index: trunk/src/org/openstreetmap/josm/data/osm/Relation.java
===================================================================
--- trunk/src/org/openstreetmap/josm/data/osm/Relation.java	(revision 13666)
+++ trunk/src/org/openstreetmap/josm/data/osm/Relation.java	(revision 13667)
@@ -41,5 +41,5 @@
 
     /**
-     *
+     * Sets members of the relation.
      * @param members Can be null, in that case all members are removed
      * @since 1925
@@ -430,17 +430,4 @@
     }
 
-    /**
-     * Determines if this relation is a boundary.
-     * @return {@code true} if a boundary relation
-     */
-    public boolean isBoundary() {
-        return "boundary".equals(get("type"));
-    }
-
-    @Override
-    public boolean isMultipolygon() {
-        return "multipolygon".equals(get("type")) || isBoundary();
-    }
-
     @Override
     public BBox getBBox() {