Fix AbstractLinkedList addAll returning true for an empty collection

src/main/java/org/apache/commons/collections4/list/AbstractLinkedList.java

@@ -588,6 +588,9 @@ public boolean addAll(final Collection<? extends E> coll) {
     @Override
     public boolean addAll(final int index, final Collection<? extends E> coll) {
         final Node<E> node = getNode(index, true);
+        if (coll.isEmpty()) {
+            return false;
+        }
         for (final E e : coll) {
             addNodeBefore(node, e);
         }

src/main/java/org/apache/commons/collections4/list/AbstractLinkedListJava21.java

@@ -592,6 +592,9 @@ public boolean addAll(final Collection<? extends E> coll) {
     @Override
     public boolean addAll(final int index, final Collection<? extends E> coll) {
         final Node<E> node = getNode(index, true);
+        if (coll.isEmpty()) {
+            return false;
+        }
         for (final E e : coll) {
             addNodeBefore(node, e);
         }

src/test/java/org/apache/commons/collections4/list/AbstractListTest.java

@@ -466,6 +466,21 @@ void testFullListSerialization() throws IOException, ClassNotFoundException {
         assertEquals(size, list2.size(), "Both lists are same size");
     }
 
+    /**
+     * Tests that {@link List#addAll(Collection)} and {@link List#addAll(int, Collection)}
+     * return false and leave the list unchanged when the collection to add is empty.
+     */
+    @Test
+    void testListAddAllEmptyReturnsFalse() {
+        if (!isAddSupported()) {
+            return;
+        }
+        final List<E> list = makeObject();
+        assertFalse(list.addAll(Collections.<E>emptyList()), "addAll of an empty collection must return false");
+        assertFalse(list.addAll(0, Collections.<E>emptyList()), "addAll(index) of an empty collection must return false");
+        assertTrue(list.isEmpty());
+    }
+
     /**
      * Tests {@link List#add(int,Object)}.
      */