1 /* 2 * Copyright (c) 2011, 2018, 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 scanning visitor of program elements with default behavior 36 * appropriate for source versions {@link SourceVersion#RELEASE_9 37 * RELEASE_9} through {@link SourceVersion#RELEASE_12 RELEASE_12}. 38 * 39 * The <code>visit<i>Xyz</i></code> methods in this 40 * class scan their component elements by calling {@code scan} on 41 * their {@linkplain Element#getEnclosedElements enclosed elements}, 42 * {@linkplain ExecutableElement#getParameters parameters}, etc., as 43 * indicated in the individual method specifications. A subclass can 44 * control the order elements are visited by overriding the 45 * <code>visit<i>Xyz</i></code> methods. Note that clients of a scanner 46 * may get the desired behavior be invoking {@code v.scan(e, p)} rather 47 * than {@code v.visit(e, p)} on the root objects of interest. 48 * 49 * <p>When a subclass overrides a <code>visit<i>Xyz</i></code> method, the 50 * new method can cause the enclosed elements to be scanned in the 51 * default way by calling <code>super.visit<i>Xyz</i></code>. In this 52 * fashion, the concrete visitor can control the ordering of traversal 53 * over the component elements with respect to the additional 54 * processing; for example, consistently calling 55 * <code>super.visit<i>Xyz</i></code> at the start of the overridden 56 * methods will yield a preorder traversal, etc. If the component 57 * elements should be traversed in some other order, instead of 58 * calling <code>super.visit<i>Xyz</i></code>, an overriding visit method 59 * should call {@code scan} with the elements in the desired order. 60 * 61 * <p> Methods in this class may be overridden subject to their 62 * general contract. Note that annotating methods in concrete 63 * subclasses with {@link java.lang.Override @Override} will help 64 * ensure that methods are overridden as intended. 65 * 66 * <p> <b>WARNING:</b> The {@code ElementVisitor} interface 67 * implemented by this class may have methods added to it in the 68 * future to accommodate new, currently unknown, language structures 69 * added to future versions of the Java™ programming language. 70 * Therefore, methods whose names begin with {@code "visit"} may be 71 * added to this class in the future; to avoid incompatibilities, 72 * classes which extend this class should not declare any instance 73 * methods with names beginning with {@code "visit"}. 74 * 75 * <p>When such a new visit method is added, the default 76 * implementation in this class will be to call the {@link 77 * #visitUnknown visitUnknown} method. A new element scanner visitor 78 * class will also be introduced to correspond to the new language 79 * level; this visitor will have different default behavior for the 80 * visit method in question. When the new visitor is introduced, all 81 * or portions of this visitor may be deprecated. 82 * 83 * @param <R> the return type of this visitor's methods. Use {@link 84 * Void} for visitors that do not need to return results. 85 * @param <P> the type of the additional parameter to this visitor's 86 * methods. Use {@code Void} for visitors that do not need an 87 * additional parameter. 88 * 89 * @see ElementScanner6 90 * @see ElementScanner7 91 * @see ElementScanner8 92 * @since 9 93 * @spec JPMS 94 */ 95 @SupportedSourceVersion(RELEASE_12) 96 public class ElementScanner9<R, P> extends ElementScanner8<R, P> { 97 /** 98 * Constructor for concrete subclasses; uses {@code null} for the 99 * default value. 100 */ 101 protected ElementScanner9(){ 102 super(null); 103 } 104 105 /** 106 * Constructor for concrete subclasses; uses the argument for the 107 * default value. 108 * 109 * @param defaultValue the default value 110 */ 111 protected ElementScanner9(R defaultValue){ 112 super(defaultValue); 113 } 114 115 /** 116 * {@inheritDoc} 117 * 118 * @implSpec This implementation scans the enclosed elements. 119 * 120 * @param e the element to visit 121 * @param p a visitor-specified parameter 122 * @return the result of the scan 123 */ 124 @Override 125 public R visitModule(ModuleElement e, P p) { 126 return scan(e.getEnclosedElements(), p); // TODO: Hmmm, this might not be right 127 } 128 }