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org.apache.commons.jexl.util.introspection.MethodMap$AmbiguousException |
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1 | /* |
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2 | * Copyright 2001,2004 The Apache Software Foundation. |
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3 | * |
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4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
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5 | * you may not use this file except in compliance with the License. |
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6 | * You may obtain a copy of the License at |
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7 | * |
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8 | * http://www.apache.org/licenses/LICENSE-2.0 |
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9 | * |
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10 | * Unless required by applicable law or agreed to in writing, software |
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11 | * distributed under the License is distributed on an "AS IS" BASIS, |
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12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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13 | * See the License for the specific language governing permissions and |
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14 | * limitations under the License. |
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15 | */ |
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16 | ||
17 | package org.apache.commons.jexl.util.introspection; |
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18 | ||
19 | import java.lang.reflect.Method; |
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20 | import java.util.ArrayList; |
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21 | import java.util.Hashtable; |
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22 | import java.util.Iterator; |
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23 | import java.util.LinkedList; |
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24 | import java.util.List; |
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25 | import java.util.Map; |
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26 | ||
27 | /** |
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28 | * |
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29 | * @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a> |
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30 | * @author <a href="mailto:bob@werken.com">Bob McWhirter</a> |
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31 | * @author <a href="mailto:Christoph.Reck@dlr.de">Christoph Reck</a> |
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32 | * @author <a href="mailto:geirm@optonline.net">Geir Magnusson Jr.</a> |
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33 | * @author <a href="mailto:szegedia@freemail.hu">Attila Szegedi</a> |
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34 | * @since 1.0 |
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35 | * @version $Id: MethodMap.java 398495 2006-05-01 01:33:43Z dion $ |
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36 | */ |
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37 | public class MethodMap { |
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38 | /** whether a method is more specific than a previously compared one. */ |
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39 | private static final int MORE_SPECIFIC = 0; |
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40 | /** whether a method is less specific than a previously compared one. */ |
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41 | private static final int LESS_SPECIFIC = 1; |
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42 | /** A method doesn't match a previously compared one. */ |
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43 | private static final int INCOMPARABLE = 2; |
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44 | ||
45 | /** |
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46 | * Keep track of all methods with the same name. |
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47 | */ |
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48 | protected Map methodByNameMap = new Hashtable(); |
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49 | ||
50 | /** |
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51 | * Add a method to a list of methods by name. For a particular class we are |
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52 | * keeping track of all the methods with the same name. |
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53 | * @param method the method. |
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54 | */ |
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55 | public void add(Method method) { |
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56 | String methodName = method.getName(); |
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57 | ||
58 | List l = get(methodName); |
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59 | ||
60 | if (l == null) { |
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61 | l = new ArrayList(); |
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62 | methodByNameMap.put(methodName, l); |
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63 | } |
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64 | ||
65 | l.add(method); |
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66 | } |
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67 | ||
68 | /** |
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69 | * Return a list of methods with the same name. |
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70 | * |
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71 | * @param key The method name. |
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72 | * @return List list of methods |
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73 | */ |
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74 | public List get(String key) { |
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75 | return (List) methodByNameMap.get(key); |
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76 | } |
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77 | ||
78 | /** |
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79 | * <p> |
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80 | * Find a method. Attempts to find the most specific applicable method using |
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81 | * the algorithm described in the JLS section 15.12.2 (with the exception |
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82 | * that it can't distinguish a primitive type argument from an object type |
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83 | * argument, since in reflection primitive type arguments are represented by |
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84 | * their object counterparts, so for an argument of type (say) |
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85 | * java.lang.Integer, it will not be able to decide between a method that |
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86 | * takes int and a method that takes java.lang.Integer as a parameter. |
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87 | * </p> |
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88 | * |
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89 | * <p> |
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90 | * This turns out to be a relatively rare case where this is needed - |
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91 | * however, functionality like this is needed. |
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92 | * </p> |
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93 | * |
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94 | * @param methodName name of method |
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95 | * @param args the actual arguments with which the method is called |
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96 | * @return the most specific applicable method, or null if no method is |
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97 | * applicable. |
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98 | * @throws AmbiguousException if there is more than one maximally specific |
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99 | * applicable method |
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100 | */ |
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101 | public Method find(String methodName, Object[] args) throws AmbiguousException { |
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102 | List methodList = get(methodName); |
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103 | ||
104 | if (methodList == null) { |
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105 | return null; |
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106 | } |
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107 | ||
108 | int l = args.length; |
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109 | Class[] classes = new Class[l]; |
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110 | ||
111 | for (int i = 0; i < l; ++i) { |
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112 | Object arg = args[i]; |
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113 | ||
114 | /* |
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115 | * if we are careful down below, a null argument goes in there so we |
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116 | * can know that the null was passed to the method |
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117 | */ |
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118 | classes[i] = arg == null ? class="keyword">null : arg.getClass(); |
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119 | } |
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120 | ||
121 | return getMostSpecific(methodList, classes); |
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122 | } |
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123 | ||
124 | /** |
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125 | * simple distinguishable exception, used when we run across ambiguous |
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126 | * overloading. |
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127 | */ |
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128 | 0 | public static class AmbiguousException extends Exception { |
129 | /** serialization version id jdk13 generated. */ |
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130 | static final long serialVersionUID = 8758118091728717367L; |
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131 | } |
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132 | ||
133 | /** |
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134 | * Gets the most specific method from a list. |
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135 | * @param methods list of {@link Method methods} |
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136 | * @param classes argument types |
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137 | * @return the most specific method, or null |
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138 | * @throws AmbiguousException if there is more than one specific method |
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139 | */ |
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140 | private static Method getMostSpecific(List methods, Class[] classes) throws AmbiguousException { |
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141 | LinkedList applicables = getApplicables(methods, classes); |
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142 | ||
143 | if (applicables.isEmpty()) { |
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144 | return null; |
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145 | } |
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146 | ||
147 | if (applicables.size() == 1) { |
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148 | return (Method) applicables.getFirst(); |
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149 | } |
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150 | ||
151 | /* |
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152 | * This list will contain the maximally specific methods. Hopefully at |
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153 | * the end of the below loop, the list will contain exactly one method, |
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154 | * (the most specific method) otherwise we have ambiguity. |
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155 | */ |
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156 | ||
157 | LinkedList maximals = new LinkedList(); |
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158 | ||
159 | for (Iterator applicable = applicables.iterator(); applicable.hasNext();) { |
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160 | Method app = (Method) applicable.next(); |
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161 | Class[] appArgs = app.getParameterTypes(); |
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162 | boolean lessSpecific = false; |
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163 | ||
164 | for (Iterator maximal = maximals.iterator(); !lessSpecific && maximal.hasNext();) { |
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165 | Method max = (Method) maximal.next(); |
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166 | ||
167 | switch (moreSpecific(appArgs, max.getParameterTypes())) { |
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168 | case MORE_SPECIFIC: |
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169 | /* |
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170 | * This method is more specific than the previously |
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171 | * known maximally specific, so remove the old maximum. |
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172 | */ |
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173 | maximal.remove(); |
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174 | break; |
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175 | ||
176 | case LESS_SPECIFIC: |
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177 | /* |
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178 | * This method is less specific than some of the |
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179 | * currently known maximally specific methods, so we |
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180 | * won't add it into the set of maximally specific |
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181 | * methods |
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182 | */ |
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183 | lessSpecific = true; |
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184 | break; |
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185 | } |
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186 | } |
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187 | ||
188 | if (!lessSpecclass="keyword">ific) { |
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189 | maximals.addLast(app); |
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190 | } |
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191 | } |
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192 | ||
193 | if (maximals.size() > 1) { |
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194 | // We have more than one maximally specific method |
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195 | throw new AmbiguousException(); |
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196 | } |
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197 | ||
198 | return (Method) maximals.getFirst(); |
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199 | } |
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200 | ||
201 | /** |
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202 | * Determines which method signature (represented by a class array) is more |
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203 | * specific. This defines a partial ordering on the method signatures. |
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204 | * |
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205 | * @param c1 first signature to compare |
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206 | * @param c2 second signature to compare |
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207 | * @return MORE_SPECIFIC if c1 is more specific than c2, LESS_SPECIFIC if c1 |
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208 | * is less specific than c2, INCOMPARABLE if they are incomparable. |
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209 | */ |
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210 | private static int moreSpecific(Class[] c1, Class[] c2) { |
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211 | boolean c1MoreSpecific = false; |
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212 | boolean c2MoreSpecific = false; |
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213 | ||
214 | for (int i = 0; i < c1.length; ++i) { |
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215 | if (c1[i] != c2[i]) { |
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216 | c1MoreSpecific = c1MoreSpecific || isStrictMethodInvocationConvertible(c2[i], c1[i]); |
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217 | c2MoreSpecific = c2MoreSpecific || isStrictMethodInvocationConvertible(c1[i], c2[i]); |
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218 | } |
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219 | } |
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220 | ||
221 | if (c1MoreSpecclass="keyword">ific) { |
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222 | if (c2MoreSpecclass="keyword">ific) { |
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223 | /* |
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224 | * Incomparable due to cross-assignable arguments (i.e. |
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225 | * foo(String, Object) vs. foo(Object, String)) |
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226 | */ |
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227 | ||
228 | return INCOMPARABLE; |
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229 | } |
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230 | ||
231 | return MORE_SPECIFIC; |
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232 | } |
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233 | ||
234 | if (c2MoreSpecclass="keyword">ific) { |
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235 | return LESS_SPECIFIC; |
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236 | } |
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237 | ||
238 | /* |
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239 | * Incomparable due to non-related arguments (i.e. foo(Runnable) vs. |
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240 | * foo(Serializable)) |
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241 | */ |
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242 | ||
243 | return INCOMPARABLE; |
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244 | } |
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245 | ||
246 | /** |
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247 | * Returns all methods that are applicable to actual argument types. |
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248 | * |
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249 | * @param methods list of all candidate methods |
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250 | * @param classes the actual types of the arguments |
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251 | * @return a list that contains only applicable methods (number of formal |
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252 | * and actual arguments matches, and argument types are assignable |
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253 | * to formal types through a method invocation conversion). |
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254 | */ |
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255 | private static LinkedList getApplicables(List methods, Class[] classes) { |
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256 | LinkedList list = new LinkedList(); |
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257 | ||
258 | for (Iterator imethod = methods.iterator(); imethod.hasNext();) { |
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259 | Method method = (Method) imethod.next(); |
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260 | ||
261 | if (isApplicable(method, classes)) { |
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262 | list.add(method); |
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263 | } |
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264 | ||
265 | } |
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266 | return list; |
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267 | } |
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268 | ||
269 | /** |
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270 | * Returns true if the supplied method is applicable to actual argument |
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271 | * types. |
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272 | * @param method the method to check |
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273 | * @param classes possible argument types |
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274 | * @return true if the arguments are applicable to the method. |
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275 | */ |
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276 | private static boolean isApplicable(Method method, Class[] classes) { |
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277 | Class[] methodArgs = method.getParameterTypes(); |
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278 | ||
279 | if (methodArgs.length != classes.length) { |
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280 | return false; |
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281 | } |
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282 | ||
283 | for (int i = 0; i < classes.length; ++i) { |
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284 | if (!isMethodInvocationConvertible(methodArgs[i], classes[i])) { |
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285 | return false; |
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286 | } |
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287 | } |
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288 | ||
289 | return true; |
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290 | } |
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291 | ||
292 | /** |
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293 | * Determines whether a type represented by a class object is convertible to |
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294 | * another type represented by a class object using a method invocation |
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295 | * conversion, treating object types of primitive types as if they were |
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296 | * primitive types (that is, a Boolean actual parameter type matches boolean |
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297 | * primitive formal type). This behavior is because this method is used to |
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298 | * determine applicable methods for an actual parameter list, and primitive |
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299 | * types are represented by their object duals in reflective method calls. |
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300 | * |
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301 | * @param formal the formal parameter type to which the actual parameter |
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302 | * type should be convertible |
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303 | * @param actual the actual parameter type. |
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304 | * @return true if either formal type is assignable from actual type, or |
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305 | * formal is a primitive type and actual is its corresponding object |
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306 | * type or an object type of a primitive type that can be converted |
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307 | * to the formal type. |
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308 | */ |
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309 | private static boolean isMethodInvocationConvertible(Class formal, Class actual) { |
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310 | /* |
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311 | * if it's a null, it means the arg was null |
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312 | */ |
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313 | if (actual == null && !formal.isPrimitive()) { |
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314 | return true; |
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315 | } |
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316 | ||
317 | /* |
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318 | * Check for identity or widening reference conversion |
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319 | */ |
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320 | ||
321 | if (actual != null && formal.isAssignableFrom(actual)) { |
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322 | return true; |
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323 | } |
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324 | ||
325 | /* |
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326 | * Check for boxing with widening primitive conversion. Note that actual |
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327 | * parameters are never primitives. |
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328 | */ |
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329 | ||
330 | if (formal.isPrimitive()) { |
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331 | if (formal == Boolean.TYPE && actual == Boolean.class) { |
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332 | return true; |
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333 | } |
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334 | if (formal == Character.TYPE && actual == Character.class) { |
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335 | return true; |
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336 | } |
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337 | if (formal == Byte.TYPE && actual == Byte.class) { |
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338 | return true; |
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339 | } |
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340 | if (formal == Short.TYPE && (actual == Short.class || actual == Byte.class)) { |
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341 | return true; |
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342 | } |
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343 | if (formal == Integer.TYPE && (actual == Integer.class || actual == Short.class || actual == Byte.class)) { |
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344 | return true; |
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345 | } |
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346 | if (formal == Long.TYPE |
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347 | && (actual == Long.class || actual == Integer.class || actual == Short.class || actual == Byte.class)) { |
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348 | return true; |
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349 | } |
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350 | if (formal == Float.TYPE |
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351 | && (actual == Float.class || actual == Long.class || actual == Integer.class |
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352 | || actual == Short.class || actual == Byte.class)) { |
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353 | return true; |
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354 | } |
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355 | if (formal == Double.TYPE |
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356 | && (actual == Double.class || actual == Float.class || actual == Long.class || actual == Integer.class |
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357 | || actual == Short.class || actual == Byte.class)) { |
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358 | return true; |
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359 | } |
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360 | } |
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361 | ||
362 | return false; |
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363 | } |
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364 | ||
365 | /** |
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366 | * Determines whether a type represented by a class object is convertible to |
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367 | * another type represented by a class object using a method invocation |
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368 | * conversion, without matching object and primitive types. This method is |
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369 | * used to determine the more specific type when comparing signatures of |
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370 | * methods. |
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371 | * |
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372 | * @param formal the formal parameter type to which the actual parameter |
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373 | * type should be convertible |
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374 | * @param actual the actual parameter type. |
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375 | * @return true if either formal type is assignable from actual type, or |
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376 | * formal and actual are both primitive types and actual can be |
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377 | * subject to widening conversion to formal. |
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378 | */ |
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379 | private static boolean isStrictMethodInvocationConvertible(Class formal, Class actual) { |
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380 | /* |
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381 | * we shouldn't get a null into, but if so |
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382 | */ |
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383 | if (actual == null && !formal.isPrimitive()) { |
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384 | return true; |
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385 | } |
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386 | ||
387 | /* |
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388 | * Check for identity or widening reference conversion |
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389 | */ |
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390 | ||
391 | if (formal.isAssignableFrom(actual)) { |
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392 | return true; |
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393 | } |
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394 | ||
395 | /* |
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396 | * Check for widening primitive conversion. |
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397 | */ |
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398 | ||
399 | if (formal.isPrimitive()) { |
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400 | if (formal == Short.TYPE && (actual == Byte.TYPE)) { |
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401 | return true; |
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402 | } |
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403 | if (formal == Integer.TYPE && (actual == Short.TYPE || actual == Byte.TYPE)) { |
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404 | return true; |
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405 | } |
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406 | if (formal == Long.TYPE && (actual == Integer.TYPE || actual == Short.TYPE || actual == Byte.TYPE)) { |
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407 | return true; |
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408 | } |
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409 | if (formal == Float.TYPE |
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410 | && (actual == Long.TYPE || actual == Integer.TYPE || actual == Short.TYPE || actual == Byte.TYPE)) { |
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411 | return true; |
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412 | } |
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413 | if (formal == Double.TYPE |
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414 | && (actual == Float.TYPE || actual == Long.TYPE || actual == Integer.TYPE || actual == Short.TYPE |
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415 | || actual == Byte.TYPE)) { |
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416 | return true; |
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417 | } |
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418 | } |
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419 | return false; |
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420 | } |
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421 | } |
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