aoqi@0: /*
aoqi@0:  * Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved.
aoqi@0:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
aoqi@0:  *
aoqi@0:  * This code is free software; you can redistribute it and/or modify it
aoqi@0:  * under the terms of the GNU General Public License version 2 only, as
aoqi@0:  * published by the Free Software Foundation.  Oracle designates this
aoqi@0:  * particular file as subject to the "Classpath" exception as provided
aoqi@0:  * by Oracle in the LICENSE file that accompanied this code.
aoqi@0:  *
aoqi@0:  * This code is distributed in the hope that it will be useful, but WITHOUT
aoqi@0:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
aoqi@0:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
aoqi@0:  * version 2 for more details (a copy is included in the LICENSE file that
aoqi@0:  * accompanied this code).
aoqi@0:  *
aoqi@0:  * You should have received a copy of the GNU General Public License version
aoqi@0:  * 2 along with this work; if not, write to the Free Software Foundation,
aoqi@0:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
aoqi@0:  *
aoqi@0:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
aoqi@0:  * or visit www.oracle.com if you need additional information or have any
aoqi@0:  * questions.
aoqi@0:  */
aoqi@0: 
aoqi@0: package javax.lang.model.util;
aoqi@0: 
aoqi@0: import javax.lang.model.element.*;
aoqi@0: import javax.annotation.processing.SupportedSourceVersion;
aoqi@0: import javax.lang.model.SourceVersion;
aoqi@0: import static javax.lang.model.SourceVersion.*;
aoqi@0: 
aoqi@0: 
aoqi@0: /**
aoqi@0:  * A scanning visitor of program elements with default behavior
aoqi@0:  * appropriate for the {@link SourceVersion#RELEASE_6 RELEASE_6}
aoqi@0:  * source version.  The <tt>visit<i>XYZ</i></tt> methods in this
aoqi@0:  * class scan their component elements by calling {@code scan} on
aoqi@0:  * their {@linkplain Element#getEnclosedElements enclosed elements},
aoqi@0:  * {@linkplain ExecutableElement#getParameters parameters}, etc., as
aoqi@0:  * indicated in the individual method specifications.  A subclass can
aoqi@0:  * control the order elements are visited by overriding the
aoqi@0:  * <tt>visit<i>XYZ</i></tt> methods.  Note that clients of a scanner
aoqi@0:  * may get the desired behavior be invoking {@code v.scan(e, p)} rather
aoqi@0:  * than {@code v.visit(e, p)} on the root objects of interest.
aoqi@0:  *
aoqi@0:  * <p>When a subclass overrides a <tt>visit<i>XYZ</i></tt> method, the
aoqi@0:  * new method can cause the enclosed elements to be scanned in the
aoqi@0:  * default way by calling <tt>super.visit<i>XYZ</i></tt>.  In this
aoqi@0:  * fashion, the concrete visitor can control the ordering of traversal
aoqi@0:  * over the component elements with respect to the additional
aoqi@0:  * processing; for example, consistently calling
aoqi@0:  * <tt>super.visit<i>XYZ</i></tt> at the start of the overridden
aoqi@0:  * methods will yield a preorder traversal, etc.  If the component
aoqi@0:  * elements should be traversed in some other order, instead of
aoqi@0:  * calling <tt>super.visit<i>XYZ</i></tt>, an overriding visit method
aoqi@0:  * should call {@code scan} with the elements in the desired order.
aoqi@0:  *
aoqi@0:  * <p> Methods in this class may be overridden subject to their
aoqi@0:  * general contract.  Note that annotating methods in concrete
aoqi@0:  * subclasses with {@link java.lang.Override @Override} will help
aoqi@0:  * ensure that methods are overridden as intended.
aoqi@0:  *
aoqi@0:  * <p> <b>WARNING:</b> The {@code ElementVisitor} interface
aoqi@0:  * implemented by this class may have methods added to it in the
aoqi@0:  * future to accommodate new, currently unknown, language structures
aoqi@0:  * added to future versions of the Java&trade; programming language.
aoqi@0:  * Therefore, methods whose names begin with {@code "visit"} may be
aoqi@0:  * added to this class in the future; to avoid incompatibilities,
aoqi@0:  * classes which extend this class should not declare any instance
aoqi@0:  * methods with names beginning with {@code "visit"}.
aoqi@0:  *
aoqi@0:  * <p>When such a new visit method is added, the default
aoqi@0:  * implementation in this class will be to call the {@link
aoqi@0:  * #visitUnknown visitUnknown} method.  A new element scanner visitor
aoqi@0:  * class will also be introduced to correspond to the new language
aoqi@0:  * level; this visitor will have different default behavior for the
aoqi@0:  * visit method in question.  When the new visitor is introduced, all
aoqi@0:  * or portions of this visitor may be deprecated.
aoqi@0:  *
aoqi@0:  * @param <R> the return type of this visitor's methods.  Use {@link
aoqi@0:  *            Void} for visitors that do not need to return results.
aoqi@0:  * @param <P> the type of the additional parameter to this visitor's
aoqi@0:  *            methods.  Use {@code Void} for visitors that do not need an
aoqi@0:  *            additional parameter.
aoqi@0:  *
aoqi@0:  * @author Joseph D. Darcy
aoqi@0:  * @author Scott Seligman
aoqi@0:  * @author Peter von der Ah&eacute;
aoqi@0:  *
aoqi@0:  * @see ElementScanner7
aoqi@0:  * @see ElementScanner8
aoqi@0:  * @since 1.6
aoqi@0:  */
aoqi@0: @SupportedSourceVersion(RELEASE_6)
aoqi@0: public class ElementScanner6<R, P> extends AbstractElementVisitor6<R, P> {
aoqi@0:     /**
aoqi@0:      * The specified default value.
aoqi@0:      */
aoqi@0:     protected final R DEFAULT_VALUE;
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * Constructor for concrete subclasses; uses {@code null} for the
aoqi@0:      * default value.
aoqi@0:      */
aoqi@0:     protected ElementScanner6(){
aoqi@0:         DEFAULT_VALUE = null;
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * Constructor for concrete subclasses; uses the argument for the
aoqi@0:      * default value.
aoqi@0:      *
aoqi@0:      * @param defaultValue the default value
aoqi@0:      */
aoqi@0:     protected ElementScanner6(R defaultValue){
aoqi@0:         DEFAULT_VALUE = defaultValue;
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * Iterates over the given elements and calls {@link
aoqi@0:      * #scan(Element, Object) scan(Element, P)} on each one.  Returns
aoqi@0:      * the result of the last call to {@code scan} or {@code
aoqi@0:      * DEFAULT_VALUE} for an empty iterable.
aoqi@0:      *
aoqi@0:      * @param iterable the elements to scan
aoqi@0:      * @param  p additional parameter
aoqi@0:      * @return the scan of the last element or {@code DEFAULT_VALUE} if no elements
aoqi@0:      */
aoqi@0:     public final R scan(Iterable<? extends Element> iterable, P p) {
aoqi@0:         R result = DEFAULT_VALUE;
aoqi@0:         for(Element e : iterable)
aoqi@0:             result = scan(e, p);
aoqi@0:         return result;
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * Processes an element by calling {@code e.accept(this, p)};
aoqi@0:      * this method may be overridden by subclasses.
aoqi@0:      *
aoqi@0:      * @param e the element to scan
aoqi@0:      * @param p a scanner-specified parameter
aoqi@0:      * @return the result of visiting {@code e}.
aoqi@0:      */
aoqi@0:     public R scan(Element e, P p) {
aoqi@0:         return e.accept(this, p);
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * Convenience method equivalent to {@code v.scan(e, null)}.
aoqi@0:      *
aoqi@0:      * @param e the element to scan
aoqi@0:      * @return the result of scanning {@code e}.
aoqi@0:      */
aoqi@0:     public final R scan(Element e) {
aoqi@0:         return scan(e, null);
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * {@inheritDoc} This implementation scans the enclosed elements.
aoqi@0:      *
aoqi@0:      * @param e  {@inheritDoc}
aoqi@0:      * @param p  {@inheritDoc}
aoqi@0:      * @return the result of scanning
aoqi@0:      */
aoqi@0:     public R visitPackage(PackageElement e, P p) {
aoqi@0:         return scan(e.getEnclosedElements(), p);
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * {@inheritDoc} This implementation scans the enclosed elements.
aoqi@0:      *
aoqi@0:      * @param e  {@inheritDoc}
aoqi@0:      * @param p  {@inheritDoc}
aoqi@0:      * @return the result of scanning
aoqi@0:      */
aoqi@0:     public R visitType(TypeElement e, P p) {
aoqi@0:         return scan(e.getEnclosedElements(), p);
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * {@inheritDoc}
aoqi@0:      *
aoqi@0:      * This implementation scans the enclosed elements, unless the
aoqi@0:      * element is a {@code RESOURCE_VARIABLE} in which case {@code
aoqi@0:      * visitUnknown} is called.
aoqi@0:      *
aoqi@0:      * @param e  {@inheritDoc}
aoqi@0:      * @param p  {@inheritDoc}
aoqi@0:      * @return the result of scanning
aoqi@0:      */
aoqi@0:     public R visitVariable(VariableElement e, P p) {
aoqi@0:         if (e.getKind() != ElementKind.RESOURCE_VARIABLE)
aoqi@0:             return scan(e.getEnclosedElements(), p);
aoqi@0:         else
aoqi@0:             return visitUnknown(e, p);
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * {@inheritDoc} This implementation scans the parameters.
aoqi@0:      *
aoqi@0:      * @param e  {@inheritDoc}
aoqi@0:      * @param p  {@inheritDoc}
aoqi@0:      * @return the result of scanning
aoqi@0:      */
aoqi@0:     public R visitExecutable(ExecutableElement e, P p) {
aoqi@0:         return scan(e.getParameters(), p);
aoqi@0:     }
aoqi@0: 
aoqi@0:     /**
aoqi@0:      * {@inheritDoc} This implementation scans the enclosed elements.
aoqi@0:      *
aoqi@0:      * @param e  {@inheritDoc}
aoqi@0:      * @param p  {@inheritDoc}
aoqi@0:      * @return the result of scanning
aoqi@0:      */
aoqi@0:     public R visitTypeParameter(TypeParameterElement e, P p) {
aoqi@0:         return scan(e.getEnclosedElements(), p);
aoqi@0:     }
aoqi@0: }