8337716: ByteBuffer hashCode implementations are inconsistent

Reviewed-by: alanb, liach

src/java.base/share/classes/java/nio/Heap-X-Buffer.java.template

@@ -29,7 +29,6 @@ package java.nio;
 
 import java.lang.foreign.MemorySegment;
 import java.util.Objects;
-import jdk.internal.util.ArraysSupport;
 
 /**
 #if[rw]
@@ -706,9 +705,6 @@ class Heap$Type$Buffer$RW$
                                                                    addr, segment)));
     }
 
-    public int hashCode() {
-        return ArraysSupport.hashCode(hb, ix(position()), remaining(), 1);
-    }
 
 #end[byte]
 
@@ -737,9 +733,6 @@ class Heap$Type$Buffer$RW$
                                       offset, segment);
     }
 
-    public int hashCode() {
-        return ArraysSupport.hashCode(hb, ix(position()), remaining(), 1);
-    }
 #end[char]
 
 

test/jdk/java/nio/Buffer/EqualsCompareTest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2017, 2024, 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
@@ -25,6 +25,7 @@ import org.testng.Assert;
 import org.testng.annotations.DataProvider;
 import org.testng.annotations.Test;
 
+import java.io.IOException;
 import java.lang.invoke.MethodHandle;
 import java.lang.invoke.MethodHandles;
 import java.lang.invoke.MethodType;
@@ -36,13 +37,21 @@ import java.nio.DoubleBuffer;
 import java.nio.FloatBuffer;
 import java.nio.IntBuffer;
 import java.nio.LongBuffer;
+import java.nio.MappedByteBuffer;
 import java.nio.ShortBuffer;
+import java.nio.channels.FileChannel;
+import java.nio.file.Files;
+import java.nio.file.Path;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.Set;
 import java.util.function.BiFunction;
 import java.util.function.LongFunction;
 import java.util.stream.IntStream;
 
+import static java.nio.charset.StandardCharsets.UTF_8;
+import static java.nio.file.StandardOpenOption.*;
+
 /*
  * @test
  * @bug 8193085 8199773
@@ -713,4 +722,17 @@ public class EqualsCompareTest {
                         .distinct().toArray();
         }
     }
+
+    @Test
+    void testHashCode() throws IOException {
+        byte[] bytes = "hello world".getBytes(UTF_8);
+        Path path = Files.createTempFile("", "");
+        Files.write(path, bytes);
+        try (FileChannel fc = FileChannel.open(path, READ, DELETE_ON_CLOSE)) {
+            MappedByteBuffer one = fc.map(FileChannel.MapMode.READ_ONLY, 0, bytes.length);
+            ByteBuffer two = ByteBuffer.wrap(bytes);
+            Assert.assertEquals(one, two);
+            Assert.assertEquals(one.hashCode(), two.hashCode());
+        }
+    }
 }

test/micro/org/openjdk/bench/java/nio/ByteBuffers.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2020, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2020, 2022, 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
@@ -923,9 +923,4 @@ public class ByteBuffers {
         }
         return r;
     }
-
-    @Benchmark
-    public int testHeapHashCode() {
-        return heapByteBuffer.hashCode();
-    }
 }