From 6b43922648fe2dfcb4cb1aaaf5d795f00a6aa174 Mon Sep 17 00:00:00 2001
From: Thomas Neidhart <tn@apache.org>
Date: Wed, 5 Feb 2014 22:10:22 +0000
Subject: [PATCH] [MATH-749] Handle case that all points are identical.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1564954 13f79535-47bb-0310-9956-ffa450edef68
---
 .../euclidean/twod/hull/GiftWrap.java         |  2 +-
 .../ConvexHullGenerator2DAbstractTest.java    | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/src/main/java/org/apache/commons/math3/geometry/euclidean/twod/hull/GiftWrap.java b/src/main/java/org/apache/commons/math3/geometry/euclidean/twod/hull/GiftWrap.java
index c46b1cac5..d02889317 100644
--- a/src/main/java/org/apache/commons/math3/geometry/euclidean/twod/hull/GiftWrap.java
+++ b/src/main/java/org/apache/commons/math3/geometry/euclidean/twod/hull/GiftWrap.java
@@ -115,7 +115,7 @@ public class GiftWrap extends AbstractConvexHullGenerator2D {
                 }
             }
             pointOnHull = nextPoint;
-        } while (nextPoint != hullVertices.get(0));
+        } while (nextPoint != hullVertices.get(0) && nextPoint != null);
 
         return hullVertices;
     }
diff --git a/src/test/java/org/apache/commons/math3/geometry/euclidean/twod/hull/ConvexHullGenerator2DAbstractTest.java b/src/test/java/org/apache/commons/math3/geometry/euclidean/twod/hull/ConvexHullGenerator2DAbstractTest.java
index 94557be95..82901466b 100644
--- a/src/test/java/org/apache/commons/math3/geometry/euclidean/twod/hull/ConvexHullGenerator2DAbstractTest.java
+++ b/src/test/java/org/apache/commons/math3/geometry/euclidean/twod/hull/ConvexHullGenerator2DAbstractTest.java
@@ -87,6 +87,18 @@ public abstract class ConvexHullGenerator2DAbstractTest {
         Assert.assertTrue(hull.getLineSegments().length == 1);
     }
 
+    @Test
+    public void testAllIdentical() {
+        final Collection<Vector2D> points = new ArrayList<Vector2D>();
+        points.add(new Vector2D(1, 1));
+        points.add(new Vector2D(1, 1));
+        points.add(new Vector2D(1, 1));
+        points.add(new Vector2D(1, 1));
+
+        final ConvexHull2D hull = generator.generate(points);
+        checkConvexHull(points, hull);
+    }
+
     @Test
     public void testConvexHull() {
         // execute 100 random variations
@@ -219,6 +231,10 @@ public abstract class ConvexHullGenerator2DAbstractTest {
         double sign = 0.0;
 
         final Vector2D[] points = hull.getVertices();
+        if (points.length < 3) {
+            return true;
+        }
+
         for (int i = 0; i < points.length; i++) {
             Vector2D p1 = points[i == 0 ? points.length - 1 : i - 1];
             Vector2D p2 = points[i];
@@ -252,6 +268,9 @@ public abstract class ConvexHullGenerator2DAbstractTest {
                                                      final boolean includesCollinearPoints) {
 
         final Collection<Vector2D> hullVertices = Arrays.asList(hull.getVertices());
+        if (hullVertices.size() < 3) {
+            return;
+        }
         final Region<Euclidean2D> region = hull.createRegion();
 
         for (final Vector2D p : points) {