1 /* |
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2 * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved. |
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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4 * |
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5 * This code is free software; you can redistribute it and/or modify it |
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6 * under the terms of the GNU General Public License version 2 only, as |
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7 * published by the Free Software Foundation. Oracle designates this |
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8 * particular file as subject to the "Classpath" exception as provided |
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9 * by Oracle in the LICENSE file that accompanied this code. |
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10 * |
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11 * This code is distributed in the hope that it will be useful, but WITHOUT |
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12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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14 * version 2 for more details (a copy is included in the LICENSE file that |
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15 * accompanied this code). |
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16 * |
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17 * You should have received a copy of the GNU General Public License version |
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18 * 2 along with this work; if not, write to the Free Software Foundation, |
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19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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20 * |
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21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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22 * or visit www.oracle.com if you need additional information or have any |
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23 * questions. |
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24 */ |
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25 |
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26 /* |
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27 * This file is available under and governed by the GNU General Public |
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28 * License version 2 only, as published by the Free Software Foundation. |
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29 * However, the following notice accompanied the original version of this |
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30 * file, and Oracle licenses the original version of this file under the BSD |
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31 * license: |
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32 */ |
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33 /* |
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34 Copyright 2009-2013 Attila Szegedi |
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35 |
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36 Licensed under both the Apache License, Version 2.0 (the "Apache License") |
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37 and the BSD License (the "BSD License"), with licensee being free to |
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38 choose either of the two at their discretion. |
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39 |
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40 You may not use this file except in compliance with either the Apache |
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41 License or the BSD License. |
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42 |
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43 If you choose to use this file in compliance with the Apache License, the |
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44 following notice applies to you: |
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45 |
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46 You may obtain a copy of the Apache License at |
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47 |
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48 http://www.apache.org/licenses/LICENSE-2.0 |
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49 |
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50 Unless required by applicable law or agreed to in writing, software |
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51 distributed under the License is distributed on an "AS IS" BASIS, |
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52 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or |
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53 implied. See the License for the specific language governing |
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54 permissions and limitations under the License. |
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55 |
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56 If you choose to use this file in compliance with the BSD License, the |
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57 following notice applies to you: |
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58 |
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59 Redistribution and use in source and binary forms, with or without |
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60 modification, are permitted provided that the following conditions are |
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61 met: |
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62 * Redistributions of source code must retain the above copyright |
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63 notice, this list of conditions and the following disclaimer. |
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64 * Redistributions in binary form must reproduce the above copyright |
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65 notice, this list of conditions and the following disclaimer in the |
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66 documentation and/or other materials provided with the distribution. |
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67 * Neither the name of the copyright holder nor the names of |
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68 contributors may be used to endorse or promote products derived from |
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69 this software without specific prior written permission. |
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70 |
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71 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS |
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72 IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED |
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73 TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A |
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74 PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER |
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75 BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
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76 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
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77 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR |
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78 BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, |
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79 WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR |
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80 OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF |
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81 ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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82 */ |
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83 |
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84 package jdk.internal.dynalink; |
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85 |
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86 import java.lang.ref.Reference; |
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87 import java.lang.ref.SoftReference; |
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88 import java.security.AccessControlContext; |
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89 import java.security.AccessController; |
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90 import java.security.PrivilegedAction; |
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91 import java.util.Map; |
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92 import java.util.WeakHashMap; |
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93 import java.util.concurrent.ConcurrentHashMap; |
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94 import java.util.concurrent.ConcurrentMap; |
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95 import jdk.internal.dynalink.internal.AccessControlContextFactory; |
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96 import jdk.internal.dynalink.internal.InternalTypeUtilities; |
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97 |
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98 /** |
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99 * A dual map that can either strongly or weakly reference a given class depending on whether the class is visible from |
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100 * a class loader or not. |
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101 * |
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102 * @param <T> the type of the values in the map |
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103 */ |
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104 abstract class ClassMap<T> { |
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105 private static final AccessControlContext GET_CLASS_LOADER_CONTEXT = |
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106 AccessControlContextFactory.createAccessControlContext("getClassLoader"); |
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107 |
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108 private final ConcurrentMap<Class<?>, T> map = new ConcurrentHashMap<>(); |
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109 private final Map<Class<?>, Reference<T>> weakMap = new WeakHashMap<>(); |
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110 private final ClassLoader classLoader; |
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111 |
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112 /** |
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113 * Creates a new class map. It will use strong references for all keys and values where the key is a class visible |
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114 * from the class loader, and will use weak keys and soft values for all other classes. |
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115 * |
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116 * @param classLoader the classloader that determines strong referenceability. |
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117 */ |
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118 ClassMap(final ClassLoader classLoader) { |
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119 this.classLoader = classLoader; |
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120 } |
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121 |
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122 /** |
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123 * Compute the value associated with the given class. It is possible that the method will be invoked several times |
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124 * (or even concurrently) for the same class parameter. |
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125 * |
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126 * @param clazz the class to compute the value for |
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127 * @return the return value. Must not be null. |
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128 */ |
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129 abstract T computeValue(Class<?> clazz); |
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130 |
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131 /** |
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132 * Returns the value associated with the class |
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133 * |
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134 * @param clazz the class |
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135 * @return the value associated with the class |
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136 */ |
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137 T get(final Class<?> clazz) { |
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138 // Check in fastest first - objects we're allowed to strongly reference |
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139 final T v = map.get(clazz); |
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140 if(v != null) { |
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141 return v; |
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142 } |
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143 // Check objects we're not allowed to strongly reference |
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144 Reference<T> ref; |
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145 synchronized(weakMap) { |
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146 ref = weakMap.get(clazz); |
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147 } |
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148 if(ref != null) { |
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149 final T refv = ref.get(); |
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150 if(refv != null) { |
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151 return refv; |
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152 } |
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153 } |
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154 // Not found in either place; create a new value |
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155 final T newV = computeValue(clazz); |
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156 assert newV != null; |
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157 |
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158 final Boolean canReferenceDirectly = AccessController.doPrivileged(new PrivilegedAction<Boolean>() { |
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159 @Override |
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160 public Boolean run() { |
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161 return InternalTypeUtilities.canReferenceDirectly(classLoader, clazz.getClassLoader()); |
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162 } |
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163 }, GET_CLASS_LOADER_CONTEXT); |
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164 |
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165 // If allowed to strongly reference, put it in the fast map |
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166 if(canReferenceDirectly) { |
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167 final T oldV = map.putIfAbsent(clazz, newV); |
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168 return oldV != null ? oldV : newV; |
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169 } |
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170 // Otherwise, put it into the weak map |
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171 synchronized(weakMap) { |
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172 ref = weakMap.get(clazz); |
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173 if(ref != null) { |
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174 final T oldV = ref.get(); |
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175 if(oldV != null) { |
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176 return oldV; |
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177 } |
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178 } |
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179 weakMap.put(clazz, new SoftReference<>(newV)); |
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180 return newV; |
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181 } |
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182 } |
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183 } |
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