add handler if neighborhood tree is null

jsprit-core/pom.xml

@@ -82,6 +82,11 @@
     	<scope>compile</scope>
     </dependency>
 
+	  <dependency>
+		  <groupId>org.apache.commons</groupId>
+		  <artifactId>commons-math3</artifactId>
+		  <version>3.4</version>
+	  </dependency>
 
   </dependencies>
   

jsprit-core/src/main/java/jsprit/core/algorithm/ruin/JobNeighborhoodsImpl.java

@@ -31,6 +31,17 @@ class JobNeighborhoodsImpl implements JobNeighborhoods {
 
     public Iterator<Job> getNearestNeighborsIterator(int nNeighbors, Job neighborTo){
         TreeSet<ReferencedJob> tree = distanceNodeTree.get(neighborTo.getId());
+        if(tree == null) return new Iterator<Job>() {
+            @Override
+            public boolean hasNext() {
+                return false;
+            }
+
+            @Override
+            public Job next() {
+                return null;
+            }
+        };
         Iterator<ReferencedJob> descendingIterator = tree.iterator();
         return new NearestNeighborhoodIterator(descendingIterator, nNeighbors);
     }

jsprit-core/src/main/java/jsprit/core/algorithm/ruin/JobNeighborhoodsImplWithCapRestriction.java

@@ -32,8 +32,24 @@ class JobNeighborhoodsImplWithCapRestriction implements JobNeighborhoods {
         logger.info("intialise " + this);
     }
 
+    /*
+    TODO: obviously nearestNeighbor does not work with a single customer
+     */
     public Iterator<Job> getNearestNeighborsIterator(int nNeighbors, Job neighborTo){
         TreeSet<ReferencedJob> tree = distanceNodeTree.get(neighborTo.getId());
+        if(tree == null) return new Iterator<Job>() {
+
+            @Override
+            public boolean hasNext() {
+                return false;
+            }
+
+            @Override
+            public Job next() {
+                return null;
+            }
+
+        };
         Iterator<ReferencedJob> descendingIterator = tree.iterator();
         return new NearestNeighborhoodIterator(descendingIterator, nNeighbors);
     }