From 06f64ca95ed4c3a9e3e8d376a619a7d3cb738e1c Mon Sep 17 00:00:00 2001
From: Jonas Holtkamp <jonas.holtkamp@senacor.com>
Date: Thu, 25 May 2017 21:17:40 +0200
Subject: [PATCH 1/2] Null-safe implementation of
 CollectionUtils#isEqualCollection

---
 .../commons/collections4/CollectionUtils.java | 20 ++++++++++++++
 .../collections4/CollectionUtilsTest.java     | 26 +++++++++++++++++++
 2 files changed, 46 insertions(+)

diff --git a/src/main/java/org/apache/commons/collections4/CollectionUtils.java b/src/main/java/org/apache/commons/collections4/CollectionUtils.java
index 5bab383dfa..f65f5c12bc 100644
--- a/src/main/java/org/apache/commons/collections4/CollectionUtils.java
+++ b/src/main/java/org/apache/commons/collections4/CollectionUtils.java
@@ -503,12 +503,21 @@ public static boolean isProperSubCollection(final Collection<?> a, final Collect
      * That is, iff the cardinality of <i>e</i> in <i>a</i> is
      * equal to the cardinality of <i>e</i> in <i>b</i>,
      * for each element <i>e</i> in <i>a</i> or <i>b</i>.
+     * <p>
+     * {@code null}s are handled without exceptions. Two {@code null}
+     * references are considered to be equal.
      *
      * @param a  the first collection, must not be null
      * @param b  the second collection, must not be null
      * @return <code>true</code> iff the collections contain the same elements with the same cardinalities.
      */
     public static boolean isEqualCollection(final Collection<?> a, final Collection<?> b) {
+        if(a == null && b == null) {
+            return true;
+        }
+        if(a == null || b == null) {
+            return false;
+        }
         if(a.size() != b.size()) {
             return false;
         }
@@ -532,6 +541,9 @@ public static boolean isEqualCollection(final Collection<?> a, final Collection<
      * equal to the cardinality of <i>e</i> in <i>b</i>,
      * for each element <i>e</i> in <i>a</i> or <i>b</i>.
      * <p>
+     * {@code null}s are handled without exceptions. Two {@code null}
+     * references are considered to be equal.
+     * <p>
      * <b>Note:</b> from version 4.1 onwards this method requires the input
      * collections and equator to be of compatible type (using bounded wildcards).
      * Providing incompatible arguments (e.g. by casting to their rawtypes)
@@ -548,6 +560,14 @@ public static boolean isEqualCollection(final Collection<?> a, final Collection<
     public static <E> boolean isEqualCollection(final Collection<? extends E> a,
                                                 final Collection<? extends E> b,
                                                 final Equator<? super E> equator) {
+        if(a == null && b == null) {
+            return true;
+        }
+
+        if(a == null || b == null) {
+            return false;
+        }
+
         if (equator == null) {
             throw new NullPointerException("Equator must not be null.");
         }
diff --git a/src/test/java/org/apache/commons/collections4/CollectionUtilsTest.java b/src/test/java/org/apache/commons/collections4/CollectionUtilsTest.java
index 0765dca8fd..70f661332e 100644
--- a/src/test/java/org/apache/commons/collections4/CollectionUtilsTest.java
+++ b/src/test/java/org/apache/commons/collections4/CollectionUtilsTest.java
@@ -559,6 +559,13 @@ public void testIsEqualCollection2() {
         assertTrue(CollectionUtils.isEqualCollection(b, a));
     }
 
+    @Test
+    public void testIsEqualCollectionWithNulls() {
+        assertTrue(CollectionUtils.isEqualCollection(null, null));
+        assertFalse(CollectionUtils.isEqualCollection(collectionA, null));
+        assertFalse(CollectionUtils.isEqualCollection(null, collectionA));
+    }
+
     @Test
     public void testIsEqualCollectionEquator() {
         final Collection<Integer> collB = CollectionUtils.collect(collectionB, TRANSFORM_TO_INTEGER);
@@ -594,6 +601,25 @@ public void testIsEqualCollectionNullEquator() {
         CollectionUtils.isEqualCollection(collectionA, collectionA, null);
     }
 
+    @Test
+    public void testIsEqualCollectionEquatorWithNulls() {
+        Equator<Object> equator = new Equator<Object>() {
+            @Override
+            public boolean equate(Object o1, Object o2) {
+                return false;
+            }
+
+            @Override
+            public int hash(Object o) {
+                return 0;
+            }
+        };
+
+        assertTrue(CollectionUtils.isEqualCollection(null, null, equator));
+        assertFalse(CollectionUtils.isEqualCollection(collectionA, null, equator));
+        assertFalse(CollectionUtils.isEqualCollection(null, collectionA, equator));
+    }
+
     @Test
     public void testIsProperSubCollection() {
         final Collection<String> a = new ArrayList<String>();

From bdaef5dfd3c705aec8271a3a33a3cf5364d0d515 Mon Sep 17 00:00:00 2001
From: Jonas Holtkamp <jonas.holtkamp@senacor.com>
Date: Sat, 27 May 2017 18:03:13 +0200
Subject: [PATCH 2/2] Removed redundant null checks in overloaded
 isEqualCollection

---
 .../apache/commons/collections4/CollectionUtils.java | 12 ------------
 1 file changed, 12 deletions(-)

diff --git a/src/main/java/org/apache/commons/collections4/CollectionUtils.java b/src/main/java/org/apache/commons/collections4/CollectionUtils.java
index f65f5c12bc..7f047e796e 100644
--- a/src/main/java/org/apache/commons/collections4/CollectionUtils.java
+++ b/src/main/java/org/apache/commons/collections4/CollectionUtils.java
@@ -560,22 +560,10 @@ public static boolean isEqualCollection(final Collection<?> a, final Collection<
     public static <E> boolean isEqualCollection(final Collection<? extends E> a,
                                                 final Collection<? extends E> b,
                                                 final Equator<? super E> equator) {
-        if(a == null && b == null) {
-            return true;
-        }
-
-        if(a == null || b == null) {
-            return false;
-        }
-
         if (equator == null) {
             throw new NullPointerException("Equator must not be null.");
         }
 
-        if(a.size() != b.size()) {
-            return false;
-        }
-
         @SuppressWarnings({ "unchecked", "rawtypes" })
         final Transformer<E, ?> transformer = new Transformer() {
             @Override