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/* * @(#)ElementScanner6.java 1.7 06/08/15 * * Copyright 2006 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ package javax.lang.model.util; import javax.lang.model.element.*; import javax.annotation.processing.SupportedSourceVersion; import static javax.lang.model.element.ElementKind.*; import javax.lang.model.SourceVersion; import static javax.lang.model.SourceVersion.*; /** * A scanning visitor of program elements with default behavior * appropriate for the {@link SourceVersion#RELEASE_6 RELEASE_6} * source version. The <tt>visit<i>XYZ</i></tt> methods in this * class scan their component elements by calling {@code scan} on * their {@linkplain Element#getEnclosedElements enclosed elements}, * {@linkplain ExecutableElement#getParameters parameters}, etc., as * indicated in the individual method specifications. A subclass can * control the order elements are visited by overriding the * <tt>visit<i>XYZ</i></tt> methods. Note that clients of a scanner * may get the desired behavior be invoking {@code v.scan(e, p)} rather * than {@code v.visit(e, p)} on the root objects of interest. * * <p>When a subclass overrides a <tt>visit<i>XYZ</i></tt> method, the * new method can cause the enclosed elements to be scanned in the * default way by calling <tt>super.visit<i>XYZ</i></tt>. In this * fashion, the concrete visitor can control the ordering of traversal * over the component elements with respect to the additional * processing; for example, consistently calling * <tt>super.visit<i>XYZ</i></tt> at the start of the overridden * methods will yield a preorder traversal, etc. If the component * elements should be traversed in some other order, instead of * calling <tt>super.visit<i>XYZ</i></tt>, an overriding visit method * should call {@code scan} with the elements in the desired order. * * <p> Methods in this class may be overridden subject to their * general contract. Note that annotating methods in concrete * subclasses with {@link java.lang.Override @Override} will help * ensure that methods are overridden as intended. * * <p> <b>WARNING:</b> The {@code ElementVisitor} interface * implemented by this class may have methods added to it in the * future to accommodate new, currently unknown, language structures * added to future versions of the Java™ programming language. * Therefore, methods whose names begin with {@code "visit"} may be * added to this class in the future; to avoid incompatibilities, * classes which extend this class should not declare any instance * methods with names beginning with {@code "visit"}. * * <p>When such a new visit method is added, the default * implementation in this class will be to call the {@link * #visitUnknown visitUnknown} method. A new element scanner visitor * class will also be introduced to correspond to the new language * level; this visitor will have different default behavior for the * visit method in question. When the new visitor is introduced, all * or portions of this visitor may be deprecated. * * @param <R> the return type of this visitor's methods. Use {@link * Void} for visitors that do not need to return results. * @param <P> the type of the additional parameter to this visitor's * methods. Use {@code Void} for visitors that do not need an * additional parameter. * * @author Joseph D. Darcy * @author Scott Seligman * @author Peter von der Ahé * @version 1.7 06/08/15 * @since 1.6 */ @SupportedSourceVersion(RELEASE_6) public class ElementScanner6<R, P> extends AbstractElementVisitor6<R, P> { /** * The specified default value. */ protected final R DEFAULT_VALUE; /** * Constructor for concrete subclasses; uses {@code null} for the * default value. */ protected ElementScanner6(){ DEFAULT_VALUE = null; } /** * Constructor for concrete subclasses; uses the argument for the * default value. */ protected ElementScanner6(R defaultValue){ DEFAULT_VALUE = defaultValue; } /** * Iterates over the given elements and calls {@link * #scan(Element, Object) scan(Element, P)} on each one. Returns * the result of the last call to {@code scan} or {@code * DEFAULT_VALUE} for an empty iterable. * * @param iterable the elements to scan * @param p additional parameter * @return the scan of the last element or {@code DEFAULT_VALUE} if no elements */ public final R scan(Iterable<? extends Element> iterable, P p) { R result = DEFAULT_VALUE; for(Element e : iterable) result = scan(e, p); return result; } /** * Processes an element by calling {@code e.accept(this, p)}; * this method may be overridden by subclasses. * @return the result of visiting {@code e}. */ public R scan(Element e, P p) { return e.accept(this, p); } /** * Convenience method equivalent to {@code v.scan(e, null)}. * @return the result of scanning {@code e}. */ public final R scan(Element e) { return scan(e, null); } /** * {@inheritDoc} This implementation scans the enclosed elements. * * @param e the element to visit * @param p a visitor-specified parameter * @return the result of scanning */ public R visitPackage(PackageElement e, P p) { return scan(e.getEnclosedElements(), p); } /** * {@inheritDoc} This implementation scans the enclosed elements. * * @param e the element to visit * @param p a visitor-specified parameter * @return the result of scanning */ public R visitType(TypeElement e, P p) { return scan(e.getEnclosedElements(), p); } /** * {@inheritDoc} This implementation scans the enclosed elements. * * @param e the element to visit * @param p a visitor-specified parameter * @return the result of scanning */ public R visitVariable(VariableElement e, P p) { return scan(e.getEnclosedElements(), p); } /** * {@inheritDoc} This implementation scans the parameters. * * @param e the element to visit * @param p a visitor-specified parameter * @return the result of scanning */ public R visitExecutable(ExecutableElement e, P p) { return scan(e.getParameters(), p); } /** * {@inheritDoc} This implementation scans the enclosed elements. * * @param e the element to visit * @param p a visitor-specified parameter * @return the result of scanning */ public R visitTypeParameter(TypeParameterElement e, P p) { return scan(e.getEnclosedElements(), p); } }