1 /* 2 * Copyright (c) 2005, 2013, 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. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package javax.lang.model.util; 27 28 import javax.lang.model.element.*; 29 import javax.annotation.processing.SupportedSourceVersion; 30 import javax.lang.model.SourceVersion; 31 import static javax.lang.model.SourceVersion.*; 32 33 34 /** 35 * A simple visitor of program elements with default behavior 36 * appropriate for the {@link SourceVersion#RELEASE_6 RELEASE_6} 37 * source version. 38 * 39 * Visit methods corresponding to {@code RELEASE_6} language 40 * constructs call {@link #defaultAction defaultAction}, passing their 41 * arguments to {@code defaultAction}'s corresponding parameters. 42 * 43 * For constructs introduced in {@code RELEASE_7} and later, {@code 44 * visitUnknown} is called instead. 45 * 46 * <p> Methods in this class may be overridden subject to their 47 * general contract. Note that annotating methods in concrete 48 * subclasses with {@link java.lang.Override @Override} will help 49 * ensure that methods are overridden as intended. 50 * 51 * <p> <b>WARNING:</b> The {@code ElementVisitor} interface 52 * implemented by this class may have methods added to it in the 53 * future to accommodate new, currently unknown, language structures 54 * added to future versions of the Java™ programming language. 55 * Therefore, methods whose names begin with {@code "visit"} may be 56 * added to this class in the future; to avoid incompatibilities, 57 * classes which extend this class should not declare any instance 58 * methods with names beginning with {@code "visit"}. 59 * 60 * <p>When such a new visit method is added, the default 61 * implementation in this class will be to call the {@link 62 * #visitUnknown visitUnknown} method. A new simple element visitor 63 * class will also be introduced to correspond to the new language 64 * level; this visitor will have different default behavior for the 65 * visit method in question. When the new visitor is introduced, all 66 * or portions of this visitor may be deprecated. 67 * 68 * <p>Note that adding a default implementation of a new visit method 69 * in a visitor class will occur instead of adding a <em>default 70 * method</em> directly in the visitor interface since a Java SE 8 71 * language feature cannot be used to this version of the API since 72 * this version is required to be runnable on Java SE 7 73 * implementations. Future versions of the API that are only required 74 * to run on Java SE 8 and later may take advantage of default methods 75 * in this situation. 76 * 77 * @param <R> the return type of this visitor's methods. Use {@code Void} 78 * for visitors that do not need to return results. 79 * @param <P> the type of the additional parameter to this visitor's methods. Use {@code Void} 80 * for visitors that do not need an additional parameter. 81 * 82 * @author Joseph D. Darcy 83 * @author Scott Seligman 84 * @author Peter von der Ahé 85 * 86 * @see SimpleElementVisitor7 87 * @see SimpleElementVisitor8 88 * @since 1.6 89 */ 90 @SupportedSourceVersion(RELEASE_6) 91 public class SimpleElementVisitor6<R, P> extends AbstractElementVisitor6<R, P> { 92 /** 93 * Default value to be returned; {@link #defaultAction 94 * defaultAction} returns this value unless the method is 95 * overridden. 96 */ 97 protected final R DEFAULT_VALUE; 98 99 /** 100 * Constructor for concrete subclasses; uses {@code null} for the 101 * default value. 102 */ 103 protected SimpleElementVisitor6(){ 104 DEFAULT_VALUE = null; 105 } 106 107 /** 108 * Constructor for concrete subclasses; uses the argument for the 109 * default value. 110 * 111 * @param defaultValue the value to assign to {@link #DEFAULT_VALUE} 112 */ 113 protected SimpleElementVisitor6(R defaultValue){ 114 DEFAULT_VALUE = defaultValue; 115 } 116 /** 117 * The default action for visit methods. The implementation in 118 * this class just returns {@link #DEFAULT_VALUE}; subclasses will 119 * commonly override this method. 120 * 121 * @param e the element to process 122 * @param p a visitor-specified parameter 123 * @return {@code DEFAULT_VALUE} unless overridden 124 */ 125 protected R defaultAction(Element e, P p) { 126 return DEFAULT_VALUE; 127 } 128 129 /** 130 * {@inheritDoc} This implementation calls {@code defaultAction}. 131 * 132 * @param e {@inheritDoc} 133 * @param p {@inheritDoc} 134 * @return the result of {@code defaultAction} 135 */ 136 public R visitPackage(PackageElement e, P p) { 137 return defaultAction(e, p); 138 } 139 140 /** 141 * {@inheritDoc} This implementation calls {@code defaultAction}. 142 * 143 * @param e {@inheritDoc} 144 * @param p {@inheritDoc} 145 * @return the result of {@code defaultAction} 146 */ 147 public R visitType(TypeElement e, P p) { 148 return defaultAction(e, p); 149 } 150 151 /** 152 * {@inheritDoc} 153 * 154 * This implementation calls {@code defaultAction}, unless the 155 * element is a {@code RESOURCE_VARIABLE} in which case {@code 156 * visitUnknown} is called. 157 * 158 * @param e {@inheritDoc} 159 * @param p {@inheritDoc} 160 * @return the result of {@code defaultAction} or {@code visitUnknown} 161 */ 162 public R visitVariable(VariableElement e, P p) { 163 if (e.getKind() != ElementKind.RESOURCE_VARIABLE) 164 return defaultAction(e, p); 165 else 166 return visitUnknown(e, p); 167 } 168 169 /** 170 * {@inheritDoc} This implementation calls {@code defaultAction}. 171 * 172 * @param e {@inheritDoc} 173 * @param p {@inheritDoc} 174 * @return the result of {@code defaultAction} 175 */ 176 public R visitExecutable(ExecutableElement e, P p) { 177 return defaultAction(e, p); 178 } 179 180 /** 181 * {@inheritDoc} This implementation calls {@code defaultAction}. 182 * 183 * @param e {@inheritDoc} 184 * @param p {@inheritDoc} 185 * @return the result of {@code defaultAction} 186 */ 187 public R visitTypeParameter(TypeParameterElement e, P p) { 188 return defaultAction(e, p); 189 } 190 }