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1 /* |
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2 * Copyright 2005-2006 Sun Microsystems, Inc. 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. Sun designates this |
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8 * particular file as subject to the "Classpath" exception as provided |
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9 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
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22 * CA 95054 USA or visit www.sun.com if you need additional information or |
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23 * have any questions. |
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24 */ |
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25 |
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26 package javax.lang.model.type; |
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27 |
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28 import javax.lang.model.element.*; |
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29 |
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30 /** |
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31 * A visitor of types, in the style of the |
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32 * visitor design pattern. Classes implementing this |
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33 * interface are used to operate on a type when the kind of |
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34 * type is unknown at compile time. When a visitor is passed to a |
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35 * type's {@link TypeMirror#accept accept} method, the <tt>visit<i>XYZ</i></tt> |
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36 * method most applicable to that type is invoked. |
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37 * |
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38 * <p> Classes implementing this interface may or may not throw a |
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39 * {@code NullPointerException} if the additional parameter {@code p} |
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40 * is {@code null}; see documentation of the implementing class for |
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41 * details. |
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42 * |
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43 * <p> <b>WARNING:</b> It is possible that methods will be added to |
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44 * this interface to accommodate new, currently unknown, language |
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45 * structures added to future versions of the Java™ programming |
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46 * language. Therefore, visitor classes directly implementing this |
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47 * interface may be source incompatible with future versions of the |
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48 * platform. To avoid this source incompatibility, visitor |
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49 * implementations are encouraged to instead extend the appropriate |
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50 * abstract visitor class that implements this interface. However, an |
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51 * API should generally use this visitor interface as the type for |
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52 * parameters, return type, etc. rather than one of the abstract |
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53 * classes. |
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54 * |
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55 * @param <R> the return type of this visitor's methods. Use {@link |
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56 * Void} for visitors that do not need to return results. |
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57 * @param <P> the type of the additional parameter to this visitor's |
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58 * methods. Use {@code Void} for visitors that do not need an |
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59 * additional parameter. |
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60 * |
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61 * @author Joseph D. Darcy |
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62 * @author Scott Seligman |
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63 * @author Peter von der Ahé |
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64 * @since 1.6 |
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65 */ |
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66 public interface TypeVisitor<R, P> { |
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67 /** |
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68 * Visits a type. |
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69 * @param t the type to visit |
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70 * @param p a visitor-specified parameter |
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71 * @return a visitor-specified result |
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72 */ |
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73 R visit(TypeMirror t, P p); |
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74 |
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75 /** |
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76 * A convenience method equivalent to {@code v.visit(t, null)}. |
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77 * @param t the element to visit |
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78 * @return a visitor-specified result |
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79 */ |
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80 R visit(TypeMirror t); |
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81 |
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82 /** |
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83 * Visits a primitive type. |
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84 * @param t the type to visit |
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85 * @param p a visitor-specified parameter |
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86 * @return a visitor-specified result |
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87 */ |
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88 R visitPrimitive(PrimitiveType t, P p); |
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89 |
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90 /** |
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91 * Visits the null type. |
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92 * @param t the type to visit |
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93 * @param p a visitor-specified parameter |
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94 * @return a visitor-specified result |
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95 */ |
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96 R visitNull(NullType t, P p); |
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97 |
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98 /** |
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99 * Visits an array type. |
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100 * @param t the type to visit |
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101 * @param p a visitor-specified parameter |
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102 * @return a visitor-specified result |
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103 */ |
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104 R visitArray(ArrayType t, P p); |
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105 |
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106 /** |
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107 * Visits a declared type. |
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108 * @param t the type to visit |
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109 * @param p a visitor-specified parameter |
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110 * @return a visitor-specified result |
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111 */ |
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112 R visitDeclared(DeclaredType t, P p); |
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113 |
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114 /** |
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115 * Visits an error type. |
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116 * @param t the type to visit |
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117 * @param p a visitor-specified parameter |
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118 * @return a visitor-specified result |
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119 */ |
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120 R visitError(ErrorType t, P p); |
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121 |
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122 /** |
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123 * Visits a type variable. |
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124 * @param t the type to visit |
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125 * @param p a visitor-specified parameter |
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126 * @return a visitor-specified result |
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127 */ |
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128 R visitTypeVariable(TypeVariable t, P p); |
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129 |
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130 /** |
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131 * Visits a wildcard type. |
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132 * @param t the type to visit |
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133 * @param p a visitor-specified parameter |
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134 * @return a visitor-specified result |
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135 */ |
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136 R visitWildcard(WildcardType t, P p); |
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137 |
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138 /** |
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139 * Visits an executable type. |
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140 * @param t the type to visit |
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141 * @param p a visitor-specified parameter |
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142 * @return a visitor-specified result |
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143 */ |
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144 R visitExecutable(ExecutableType t, P p); |
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145 |
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146 /** |
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147 * Visits a {@link NoType} instance. |
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148 * @param t the type to visit |
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149 * @param p a visitor-specified parameter |
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150 * @return a visitor-specified result |
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151 */ |
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152 R visitNoType(NoType t, P p); |
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153 |
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154 /** |
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155 * Visits an unknown kind of type. |
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156 * This can occur if the language evolves and new kinds |
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157 * of types are added to the {@code TypeMirror} hierarchy. |
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158 * @param t the type to visit |
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159 * @param p a visitor-specified parameter |
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160 * @return a visitor-specified result |
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161 * @throws UnknownTypeException |
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162 * a visitor implementation may optionally throw this exception |
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163 */ |
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164 R visitUnknown(TypeMirror t, P p); |
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165 } |