1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   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
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  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
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  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 
  46         // This is the initial size of Character.UnicodeBlock.map
  47         // See src/java.base/share/classes/java/lang/Character.java
  48         int initialCapacity = (int)(510 / 0.75f + 1.0f);
  49 
  50         // We will check that the capacity was sufficient:
  51         // - create a new HashMap with this initial capacity
  52         // - insert map.size() elements in it
  53         // - check that the internal storage wasn't reallocated
  54 
  55         // Construct a HashMap with specified initial capacity
  56         HashMap<Object,Object> map1 = new HashMap<>(initialCapacity);
  57         Class<?> hmCls = HashMap.class;
  58         Field tableField = hmCls.getDeclaredField("table");
  59         tableField.setAccessible(true);
  60         // ... and fill it up
  61         map1.put(new Object(), new Object());
  62         final Object initialTable = tableField.get(map1);
  63         while (map1.size() < map.size() &&
  64                 initialTable == tableField.get(map1)) {
  65             map1.put(new Object(), new Object());
  66         }
  67 
  68         // Now check that internal storage didn't change
  69         if (initialTable != tableField.get(map1)) {
  70             throw new RuntimeException(
  71                     "Initial capacity " + INITIAL_CAPACITY +
  72                     " was only enough to hold " + (map1.size()-1) +
  73                     " entries, but needed " + map.size());
  74         }
  75     }
  76 }