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 // This is the initial size of Character.UnicodeBlock.map 48 // See src/java.base/share/classes/java/lang/Character.java 49 int INITIAL_CAPACITY = 680; //(int)(510 / 0.75f + 1.0f); 50 51 // We will check that the capacity was sufficient: 52 // - create a new HashMap with this initial capacity 53 // - insert map.size() elements in it 54 // - check that the internal storage wasn't reallocated 55 56 // Construct a HashMap with specified initial capacity 57 HashMap<Object,Object> map1 = new HashMap<>(INITIAL_CAPACITY); 58 Class<?> hmCls = HashMap.class; 59 Field tableField = hmCls.getDeclaredField("table"); 60 tableField.setAccessible(true); 61 // ... and fill it up 62 map1.put(new Object(), new Object()); 63 final Object initialTable = tableField.get(map1); 64 while (map1.size() < map.size() && 65 initialTable == tableField.get(map1)) { 66 map1.put(new Object(), new Object()); 67 } 68 69 // Now check that internal storage didn't change 70 if (initialTable != tableField.get(map1)) { 71 throw new RuntimeException( 72 "Initial capacity " + INITIAL_CAPACITY + 73 " was only enough to hold " + (map1.size()-1) + 74 " entries, but needed " + map.size()); 75 } 76 } 77 }