8259622: TreeMap.computeIfAbsent deviates from spec

Reviewed-by: smarks
openjdk · Jan 15, 2021 · 2c8e337 · 2c8e337 · openjdk-notifier · Jan 15, 2021
1 parent d701bab
commit 2c8e337
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Showing 2 changed files with 26 additions and 4 deletions.
diff --git a/src/java.base/share/classes/java/util/TreeMap.java b/src/java.base/share/classes/java/util/TreeMap.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2021, 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
@@ -575,8 +575,12 @@ public V computeIfAbsent(K key, Function<? super K, ? extends V> mappingFunction
                     t = t.left;
                 else if (cmp > 0)
                     t = t.right;
-                else
+                else {
+                    if (t.value == null) {
+                        t.value = callMappingFunctionWithCheck(key, mappingFunction);
+                    }
                     return t.value;
+                }
             } while (t != null);
         } else {
             Objects.requireNonNull(key);
@@ -589,8 +593,12 @@ else if (cmp > 0)
                     t = t.left;
                 else if (cmp > 0)
                     t = t.right;
-                else
+                else {
+                    if (t.value == null) {
+                        t.value = callMappingFunctionWithCheck(key, mappingFunction);
+                    }
                     return t.value;
+                }
             } while (t != null);
         }
         newValue = callMappingFunctionWithCheck(key, mappingFunction);

diff --git a/test/jdk/java/util/Map/InPlaceOpsCollisions.java b/test/jdk/java/util/Map/InPlaceOpsCollisions.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2013, 2021, 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
@@ -257,6 +257,20 @@ void testComputeIfAbsentNull(String desc, Supplier<Map<Object, Object>> ms, Obje
         testComputeIfAbsent(map, desc, keys, (k) -> null);
     }
 
+    @Test(dataProvider = "nullValueFriendlyMaps")
+    void testComputeIfAbsentOverwriteNull(String desc, Supplier<Map<Object, Object>> ms) {
+        Map<Object, Object> map = ms.get();
+        map.put("key", null);
+        assertEquals(map.size(), 1, desc + ": size != 1");
+        assertTrue(map.containsKey("key"), desc + ": does not have key");
+        assertNull(map.get("key"), desc + ": value is not null");
+        Object result = map.computeIfAbsent("key", k -> "value"); // must rewrite
+        assertEquals(result, "value", desc + ": computeIfAbsent result is not 'value'");
+        assertEquals(map.size(), 1, desc + ": size != 1");
+        assertTrue(map.containsKey("key"), desc + ": does not have key");
+        assertEquals(map.get("key"), "value", desc + ": value is not 'value'");
+    }
+
     private static <T> void testComputeIfPresent(Map<T, T> map, String desc, T[] keys,
             BiFunction<T, T, T> mappingFunction) {
         // remove a third of the keys