1 /*
   2  * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 
  24 
  25 /**
  26  * @test
  27  * @bug 8080535
  28  * @summary Expected size of Character.UnicodeBlock.map is not optimal
  29  */
  30 
  31 import java.lang.reflect.Field;
  32 import java.util.HashMap;
  33 import java.util.Map;
  34 
  35 public class NonOptimalMapSize {
  36     public static void main(String[] args) throws Throwable {
  37         Class<?> ubCls = Character.UnicodeBlock.class;
  38         Field mapField = ubCls.getDeclaredField("map");
  39         mapField.setAccessible(true);
  40         Map<?,?> map = (Map<?,?>)mapField.get(null);
  41         if (!map.getClass().equals(HashMap.class)) {
  42             throw new RuntimeException(
  43                     "Character.UnicodeBlock.map is expected to be HashMap");
  44         }
  45         int mapSize = map.size();
  46 
  47         Field sizeField = ubCls.getDeclaredField("INITIAL_CAPACITY");
  48         sizeField.setAccessible(true);
  49         int INITIAL_CAPACITY = sizeField.getInt(null);
  50 
  51         // Construct a HashMap with specified initial capacity
  52         HashMap<Object,Object> map1 = new HashMap<>(INITIAL_CAPACITY);
  53         Class<?> hmCls = HashMap.class;
  54         Field tableField = hmCls.getDeclaredField("table");
  55         tableField.setAccessible(true);
  56         // ... and fill it up
  57         map1.put(new Object(), new Object());
  58         final Object initialTable = tableField.get(map1);
  59         while (map1.size() < map.size() &&
  60                 initialTable == tableField.get(map1)) {
  61             map1.put(new Object(), new Object());
  62         }
  63 
  64         // Now check that internal storage didn't change
  65         if (initialTable != tableField.get(map1)) {
  66             throw new RuntimeException(
  67                     "Initial capacity " + INITIAL_CAPACITY +
  68                     " was only enough to hold " + (map1.size()-1) +
  69                     " entries, but needed " + map.size());
  70         }
  71     }
  72 }