Java example source code file (ElementScanner7.java)

This example Java source code file (ElementScanner7.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

elementscanner6, elementscanner7, override, supportedsourceversion

The ElementScanner7.java Java example source code

/*
 * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package javax.lang.model.util;

import javax.lang.model.element.*;
import javax.annotation.processing.SupportedSourceVersion;
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_7 RELEASE_7}
 * source version.  The <tt>visitXYZ 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>visitXYZ 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 visitXYZ method, the
 * new method can cause the enclosed elements to be scanned in the
 * default way by calling <tt>super.visitXYZ.  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.visitXYZ 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.visitXYZ, 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> WARNING: 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.
 *
 * @see ElementScanner6
 * @see ElementScanner8
 * @since 1.7
 */
@SupportedSourceVersion(RELEASE_7)
public class ElementScanner7<R, P> extends ElementScanner6 {
    /**
     * Constructor for concrete subclasses; uses {@code null} for the
     * default value.
     */
    protected ElementScanner7(){
        super(null);
    }

    /**
     * Constructor for concrete subclasses; uses the argument for the
     * default value.
     *
     * @param defaultValue the default value
     */
    protected ElementScanner7(R defaultValue){
        super(defaultValue);
    }

    /**
     * This implementation scans the enclosed elements.
     *
     * @param e  {@inheritDoc}
     * @param p  {@inheritDoc}
     * @return the result of scanning
     */
    @Override
    public R visitVariable(VariableElement e, P p) {
        return scan(e.getEnclosedElements(), p);
    }
}