8080535: (ch) Expected size of Character.UnicodeBlock.map is not optimal

Reviewed-by: martin, chegar

jdk/src/java.base/share/classes/java/lang/Character.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2002, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2002, 2015, 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
@@ -645,8 +645,14 @@ class Character implements java.io.Serializable, Comparable<Character> {
      * @since 1.2
      */
     public static final class UnicodeBlock extends Subset {
-
+        /**
-        private static Map<String, UnicodeBlock> map = new HashMap<>(256);
+         * 510  - the expected number of enteties
+         * 0.75 - the default load factor of HashMap
+         */
+        private static final int INITIAL_CAPACITY =
+                (int)(510 / 0.75f + 1.0f);
+        private static Map<String, UnicodeBlock> map =
+                new HashMap<>(INITIAL_CAPACITY);
 
         /**
          * Creates a UnicodeBlock with the given identifier name.

jdk/test/java/lang/Character/UnicodeBlock/NonOptimalMapSize.java

@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2015, 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 8080535
+ * @summary Expected size of Character.UnicodeBlock.map is not optimal
+ */
+
+import java.lang.reflect.Field;
+import java.util.HashMap;
+import java.util.Map;
+
+public class NonOptimalMapSize {
+    public static void main(String[] args) throws Throwable {
+        Class<?> ubCls = Character.UnicodeBlock.class;
+        Field mapField = ubCls.getDeclaredField("map");
+        mapField.setAccessible(true);
+        Map<?,?> map = (Map<?,?>)mapField.get(null);
+        if (!map.getClass().equals(HashMap.class)) {
+            throw new RuntimeException(
+                    "Character.UnicodeBlock.map is expected to be HashMap");
+        }
+        int mapSize = map.size();
+
+        Field sizeField = ubCls.getDeclaredField("INITIAL_CAPACITY");
+        sizeField.setAccessible(true);
+        int INITIAL_CAPACITY = sizeField.getInt(null);
+
+        // Construct a HashMap with specified initial capacity
+        HashMap<Object,Object> map1 = new HashMap<>(INITIAL_CAPACITY);
+        Class<?> hmCls = HashMap.class;
+        Field tableField = hmCls.getDeclaredField("table");
+        tableField.setAccessible(true);
+        // ... and fill it up
+        map1.put(new Object(), new Object());
+        final Object initialTable = tableField.get(map1);
+        while (map1.size() < map.size() &&
+                initialTable == tableField.get(map1)) {
+            map1.put(new Object(), new Object());
+        }
+
+        // Now check that internal storage didn't change
+        if (initialTable != tableField.get(map1)) {
+            throw new RuntimeException(
+                    "Initial capacity " + INITIAL_CAPACITY +
+                    " was only enough to hold " + (map1.size()-1) +
+                    " entries, but needed " + map.size());
+        }
+    }
+}