(commons-collections) branch master updated: Increment modCount after the bounds check in TreeList add and remove (#716)

[ggregory]

This is an automated email from the ASF dual-hosted git repository.

garydgregory pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/commons-collections.git


The following commit(s) were added to refs/heads/master by this push:
     new fe8eb4989 Increment modCount after the bounds check in TreeList add 
and remove (#716)
fe8eb4989 is described below

commit fe8eb4989392cb436438978b151aa800b70195b9
Author: Naveed Khan <164054284+rootvect...@users.noreply.github.com>
AuthorDate: Wed Jul 22 14:05:17 2026 +0000

    Increment modCount after the bounds check in TreeList add and remove (#716)
    
    a rejected index left modCount advanced, invalidating a live iterator with 
a spurious ConcurrentModificationException.
---
 .../apache/commons/collections4/list/TreeList.java    |  4 ++--
 .../commons/collections4/list/TreeListTest.java       | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/src/main/java/org/apache/commons/collections4/list/TreeList.java 
b/src/main/java/org/apache/commons/collections4/list/TreeList.java
index d2e75eba4..68931b2ca 100644
--- a/src/main/java/org/apache/commons/collections4/list/TreeList.java
+++ b/src/main/java/org/apache/commons/collections4/list/TreeList.java
@@ -966,8 +966,8 @@ public class TreeList<E> extends AbstractList<E> {
      */
     @Override
     public void add(final int index, final E obj) {
-        modCount++;
         checkInterval(index, 0, size());
+        modCount++;
         if (root == null) {
             root = new AVLNode<>(index, obj, null, null);
         } else {
@@ -1105,8 +1105,8 @@ public class TreeList<E> extends AbstractList<E> {
      */
     @Override
     public E remove(final int index) {
-        modCount++;
         checkInterval(index, 0, size() - 1);
+        modCount++;
         final E result = get(index);
         root = root.remove(index);
         size--;
diff --git 
a/src/test/java/org/apache/commons/collections4/list/TreeListTest.java 
b/src/test/java/org/apache/commons/collections4/list/TreeListTest.java
index bff75d2bc..2f2adf05c 100644
--- a/src/test/java/org/apache/commons/collections4/list/TreeListTest.java
+++ b/src/test/java/org/apache/commons/collections4/list/TreeListTest.java
@@ -171,6 +171,25 @@ public class TreeListTest<E> extends AbstractListTest<E> {
         assertEquals("A", li.previous());
     }
 
+    @Test
+    void testFailedIndexedChangeKeepsIteratorValid() {
+        final List<String> list = new TreeList<>();
+        list.add("a");
+        list.add("b");
+
+        // a rejected add(index) is a no-op and must not invalidate a live 
iterator
+        final ListIterator<String> addIt = list.listIterator();
+        assertThrows(IndexOutOfBoundsException.class, () -> list.add(5, "x"));
+        assertEquals(2, list.size());
+        assertEquals("a", addIt.next());
+
+        // same for a rejected remove(index)
+        final ListIterator<String> removeIt = list.listIterator();
+        assertThrows(IndexOutOfBoundsException.class, () -> list.remove(10));
+        assertEquals(2, list.size());
+        assertEquals("a", removeIt.next());
+    }
+
     @Test
     @SuppressWarnings("unchecked")
     void testIndexOf() {