From 7ea9a9e84941bb453a006e7035c48f344e0d1d6a Mon Sep 17 00:00:00 2001
From: Viktor Klang <viktor.klang@oracle.com>
Date: Fri, 21 Nov 2025 15:22:02 +0100
Subject: [PATCH] Addressing 8372256 by catching CCE and NPE during invocation
 to Map::get in CHM::equals

---
 .../util/concurrent/ConcurrentHashMap.java    | 18 +++++++++++++-----
 .../concurrent/tck/ConcurrentHashMapTest.java | 19 +++++++++++++++++++
 2 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/src/java.base/share/classes/java/util/concurrent/ConcurrentHashMap.java b/src/java.base/share/classes/java/util/concurrent/ConcurrentHashMap.java
index 4cb7048a798e3..9295f0deb59b8 100644
--- a/src/java.base/share/classes/java/util/concurrent/ConcurrentHashMap.java
+++ b/src/java.base/share/classes/java/util/concurrent/ConcurrentHashMap.java
@@ -1372,12 +1372,20 @@ public boolean equals(Object o) {
             Node<K,V>[] t;
             int f = (t = table) == null ? 0 : t.length;
             Traverser<K,V> it = new Traverser<K,V>(t, f, 0, f);
-            for (Node<K,V> p; (p = it.advance()) != null; ) {
-                V val = p.val;
-                Object v = m.get(p.key);
-                if (v == null || (v != val && !v.equals(val)))
-                    return false;
+
+            try {
+                for (Node<K,V> p; (p = it.advance()) != null; ) {
+                    V val = p.val;
+                    Object v = m.get(p.key);
+                    if (v == null || (v != val && !v.equals(val)))
+                        return false;
+                }
+            } catch (ClassCastException | NullPointerException _) {
+                // m.get(p.key) is contractually allowed to throw CCE or NPE
+                // but CHM doesn't allow null keys, so NPE shouldn't occur in practice
+                return false;
             }
+
             for (Map.Entry<?,?> e : m.entrySet()) {
                 Object mk, mv, v;
                 if ((mk = e.getKey()) == null ||
diff --git a/test/jdk/java/util/concurrent/tck/ConcurrentHashMapTest.java b/test/jdk/java/util/concurrent/tck/ConcurrentHashMapTest.java
index c87571b01f7b3..168594832c2f8 100644
--- a/test/jdk/java/util/concurrent/tck/ConcurrentHashMapTest.java
+++ b/test/jdk/java/util/concurrent/tck/ConcurrentHashMapTest.java
@@ -40,6 +40,7 @@
 import java.util.Collections;
 import java.util.Enumeration;
 import java.util.Iterator;
+import java.util.HashMap;
 import java.util.Map;
 import java.util.Random;
 import java.util.Set;
@@ -878,6 +879,24 @@ public void testReentrantComputeIfAbsent() {
         } catch (IllegalStateException success) {}
     }
 
+    public void testMapEqualsIfClassCastExceptionOccurs() {
+        class MonotypeKeyMap extends HashMap<Byte, Object> {
+            @Override public Object get(Object key) {
+                return super.get((Byte)key); // Force cast, allowed by spec
+            }
+        }
+
+        var mkm = new MonotypeKeyMap();
+        mkm.put((byte)1, "value1");
+        var similar = new ConcurrentHashMap<Byte, Object>();
+        similar.put((byte)1, "value1");
+        var different = new ConcurrentHashMap<String, String>();
+        different.put("test1", "value1");
+
+        assertTrue(similar.equals(mkm));
+        assertFalse(different.equals(mkm));
+    }
+
     private static Item findValue(ConcurrentHashMap<Item, Item> map,
                                   Item key) {
         return (key.value % 5 == 0) ?  key :