8046085: inserting null key into HashMap treebin fails

Co-authored-by: Paul Sandoz <paul.sandoz@oracle.com>
Reviewed-by: dl, mduigou, alanb, chegar

jdk/src/share/classes/java/util/HashMap.java

@@ -1967,7 +1967,7 @@ public class HashMap<K,V> extends AbstractMap<K,V>
                     dir = -1;
                 else if (ph < h)
                     dir = 1;
-                else if ((pk = p.key) == k || (pk != null && k.equals(pk)))
+                else if ((pk = p.key) == k || (k != null && k.equals(pk)))
                     return p;
                 else if ((kc == null &&
                           (kc = comparableClassFor(k)) == null) ||

jdk/test/java/util/HashMap/PutNullKey.java

@@ -0,0 +1,90 @@
+/*
+ * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/**
+ * @test
+ * @bug 8046085
+ * @summary Ensure that when trees are being used for collisions that null key
+ * insertion still works.
+ */
+
+import java.util.*;
+import java.util.stream.IntStream;
+
+public class PutNullKey {
+
+    // Initial capacity of map
+    // Should be >= the map capacity for treeifying, see HashMap/ConcurrentMap.MIN_TREEIFY_CAPACITY
+    static final int INITIAL_CAPACITY = 64;
+
+    // Maximum size of map
+    // Should be > the treeify threshold, see HashMap/ConcurrentMap.TREEIFY_THRESHOLD
+    static final int SIZE = 256;
+
+    // Load factor of map
+    // A value 1.0 will ensure that a new threshold == capacity
+    static final float LOAD_FACTOR = 1.0f;
+
+    public static class CollidingHash implements Comparable<CollidingHash> {
+
+        private final int value;
+
+        public CollidingHash(int value) {
+            this.value = value;
+        }
+
+        @Override
+        public int hashCode() {
+            // intentionally bad hashcode. Force into first bin.
+            return 0;
+        }
+
+        @Override
+        public boolean equals(Object o) {
+            if (null == o) {
+                return false;
+            }
+
+            if (o.getClass() != CollidingHash.class) {
+                return false;
+            }
+
+            return value == ((CollidingHash) o).value;
+        }
+
+        @Override
+        public int compareTo(CollidingHash o) {
+            return value - o.value;
+        }
+    }
+
+    public static void main(String[] args) throws Exception {
+        Map<Object,Object> m = new HashMap<>(INITIAL_CAPACITY, LOAD_FACTOR);
+        IntStream.range(0, SIZE)
+                .mapToObj(CollidingHash::new)
+                .forEach(e -> { m.put(e, e); });
+
+        // kaboom?
+        m.put(null, null);
+    }
+}