1 /* 2 * Copyright (c) 2019, 2020, 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 java.util.List; 29 import java.util.ArrayList; 30 import javax.lang.model.element.*; 31 import javax.annotation.processing.SupportedSourceVersion; 32 import javax.lang.model.SourceVersion; 33 import static javax.lang.model.SourceVersion.*; 34 35 /** 36 * {@preview Associated with records, a preview feature of the Java language. 37 * 38 * This class is associated with <i>records</i>, a preview 39 * feature of the Java language. Preview features 40 * may be removed in a future release, or upgraded to permanent 41 * features of the Java language.} 42 * 43 * A scanning visitor of program elements with default behavior 44 * appropriate for the {@link SourceVersion#RELEASE_14 RELEASE_14} 45 * source version. 46 * 47 * The <code>visit<i>Xyz</i></code> methods in this 48 * class scan their component elements by calling {@code scan} on 49 * their {@linkplain Element#getEnclosedElements enclosed elements}, 50 * {@linkplain ExecutableElement#getParameters parameters}, etc., as 51 * indicated in the individual method specifications. A subclass can 52 * control the order elements are visited by overriding the 53 * <code>visit<i>Xyz</i></code> methods. Note that clients of a scanner 54 * may get the desired behavior be invoking {@code v.scan(e, p)} rather 55 * than {@code v.visit(e, p)} on the root objects of interest. 56 * 57 * <p>When a subclass overrides a <code>visit<i>Xyz</i></code> method, the 58 * new method can cause the enclosed elements to be scanned in the 59 * default way by calling <code>super.visit<i>Xyz</i></code>. In this 60 * fashion, the concrete visitor can control the ordering of traversal 61 * over the component elements with respect to the additional 62 * processing; for example, consistently calling 63 * <code>super.visit<i>Xyz</i></code> at the start of the overridden 64 * methods will yield a preorder traversal, etc. If the component 65 * elements should be traversed in some other order, instead of 66 * calling <code>super.visit<i>Xyz</i></code>, an overriding visit method 67 * should call {@code scan} with the elements in the desired order. 68 * 69 * @apiNote 70 * Methods in this class may be overridden subject to their general 71 * contract. 72 * 73 * @param <R> the return type of this visitor's methods. Use {@link 74 * Void} for visitors that do not need to return results. 75 * @param <P> the type of the additional parameter to this visitor's 76 * methods. Use {@code Void} for visitors that do not need an 77 * additional parameter. 78 * 79 * @see <a href="ElementScanner6.html#note_for_subclasses"><strong>Compatibility note for subclasses</strong></a> 80 * @see ElementScanner6 81 * @see ElementScanner7 82 * @see ElementScanner8 83 * @see ElementScanner9 84 * @since 14 85 */ 86 @jdk.internal.PreviewFeature(feature=jdk.internal.PreviewFeature.Feature.RECORDS, 87 essentialAPI=false) 88 @SupportedSourceVersion(RELEASE_15) 89 public class ElementScanner14<R, P> extends ElementScanner9<R, P> { 90 /** 91 * Constructor for concrete subclasses; uses {@code null} for the 92 * default value. 93 */ 94 protected ElementScanner14(){ 95 super(null); 96 } 97 98 /** 99 * Constructor for concrete subclasses; uses the argument for the 100 * default value. 101 * 102 * @param defaultValue the default value 103 */ 104 protected ElementScanner14(R defaultValue){ 105 super(defaultValue); 106 } 107 108 /** 109 * {@inheritDoc} 110 * 111 * @implSpec This implementation scans the type parameters, if 112 * any, and then the enclosed elements. 113 * 114 * 115 * @param e {@inheritDoc} 116 * @param p {@inheritDoc} 117 * @return the result of scanning 118 */ 119 @Override 120 public R visitType(TypeElement e, P p) { 121 return scan(createScanningList(e, e.getEnclosedElements()), p); 122 } 123 124 /** 125 * {@inheritDoc} 126 * 127 * @implSpec This implementation first scans the type parameters, if any, and then 128 * the parameters. 129 * 130 * @param e {@inheritDoc} 131 * @param p {@inheritDoc} 132 * @return the result of scanning 133 */ 134 public R visitExecutable(ExecutableElement e, P p) { 135 return scan(createScanningList(e, e.getParameters()), p); 136 } 137 138 private List<? extends Element> createScanningList(Parameterizable element, 139 List<? extends Element> toBeScanned) { 140 var typeParameters = element.getTypeParameters(); 141 if (typeParameters.isEmpty()) { 142 return toBeScanned; 143 } else { 144 List<Element> scanningList = new ArrayList<>(typeParameters); 145 scanningList.addAll(toBeScanned); 146 return scanningList; 147 } 148 } 149 150 /** 151 * {@inheritDoc} 152 * 153 * @implSpec This implementation scans the enclosed elements. 154 * 155 * @param e the element to visit 156 * @param p a visitor-specified parameter 157 * @return the result of the scan 158 */ 159 @SuppressWarnings("preview") 160 @Override 161 public R visitRecordComponent(RecordComponentElement e, P p) { 162 return scan(e.getEnclosedElements(), p); 163 } 164 }