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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 RELEASE_6 source version. The visitXyz methods in this class scan their component elements by calling scan on their enclosed elements, parameters, etc., as indicated in the individual method specifications. A subclass can control the order elements are visited by overriding the visitXyz methods. Note that clients of a scanner may get the desired behavior be invoking v.scan(e, p) rather than v.visit(e, p) on the root objects of interest. 
When a subclass overrides a visitXyz method, the
new method can cause the enclosed elements to be scanned in the
default way by calling 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
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 super.visitXyz, an overriding visit method should call scan with the elements in the desired order. 
 Methods in this class may be overridden subject to their general contract. Note that annotating methods in concrete subclasses with @Override will help ensure that methods are overridden as intended. 
 WARNING: The 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 "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 "visit". 
When such a new visit method is added, the default implementation in this class will be to call the 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. 
Author:
Joseph D. Darcy, Scott Seligman, Peter von der Ahé
Type parameters:
<R> – the return type of this visitor's methods. Use Void for visitors that do not need to return results.
<P> – the type of the additional parameter to this visitor's methods. Use Void for visitors that do not need an additional parameter.
See Also:
ElementScanner7
ElementScanner8
ElementScanner9
Since:
1.6/**
 * A scanning visitor of program elements with default behavior
 * appropriate for the {@link SourceVersion#RELEASE_6 RELEASE_6}
 * source version.  The <code>visit<i>Xyz</i></code> 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
 * <code>visit<i>Xyz</i></code> 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 <code>visit<i>Xyz</i></code> method, the
 * new method can cause the enclosed elements to be scanned in the
 * default way by calling <code>super.visit<i>Xyz</i></code>.  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
 * <code>super.visit<i>Xyz</i></code> 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 <code>super.visit<i>Xyz</i></code>, 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&trade; 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 Ah&eacute;
 *
 * @see ElementScanner7
 * @see ElementScanner8
 * @see ElementScanner9
 * @since 1.6
 */
@SupportedSourceVersion(RELEASE_6)
public class ElementScanner6<R, P> extends AbstractElementVisitor6<R, P> {
    
The specified default value.
/**
     * The specified default value.
     */
    protected final R DEFAULT_VALUE;

    
Constructor for concrete subclasses; uses null for the default value. 
Deprecated:
Release 6 is obsolete; update to a visitor for a newer
release level./**
     * Constructor for concrete subclasses; uses {@code null} for the
     * default value.
     * @deprecated Release 6 is obsolete; update to a visitor for a newer
     * release level.
     */
    @Deprecated(since="9")
    protected ElementScanner6(){
        DEFAULT_VALUE = null;
    }

    
Constructor for concrete subclasses; uses the argument for the
default value.
Params:
defaultValue – the default value
Deprecated:
Release 6 is obsolete; update to a visitor for a newer
release level./**
     * Constructor for concrete subclasses; uses the argument for the
     * default value.
     *
     * @param defaultValue the default value
     * @deprecated Release 6 is obsolete; update to a visitor for a newer
     * release level.
     */
    @Deprecated(since="9")
    protected ElementScanner6(R defaultValue){
        DEFAULT_VALUE = defaultValue;
    }

    
Iterates over the given elements and calls scan(Element, P) on each one. Returns the result of the last call to scan or 
DEFAULT_VALUE for an empty iterable. 
Params:
iterable – the elements to scan
p – additional parameter
Returns:
the scan of the last element or DEFAULT_VALUE if no elements/**
     * 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 e.accept(this, p); this method may be overridden by subclasses. 
Params:
e – the element to scan
p – a scanner-specified parameter
Returns:
the result of visiting e./**
     * Processes an element by calling {@code e.accept(this, p)};
     * this method may be overridden by subclasses.
     *
     * @param e the element to scan
     * @param p a scanner-specified parameter
     * @return the result of visiting {@code e}.
     */
    public R scan(Element e, P p) {
        return e.accept(this, p);
    }

    
Convenience method equivalent to v.scan(e, null). 
Params:
e – the element to scan
Returns:
the result of scanning e./**
     * Convenience method equivalent to {@code v.scan(e, null)}.
     *
     * @param e the element to scan
     * @return the result of scanning {@code e}.
     */
    public final R scan(Element e) {
        return scan(e, null);
    }

    
{@inheritDoc}
Params:
e –  {@inheritDoc}
p –  {@inheritDoc}
Implementation Requirements:
This implementation scans the enclosed elements.
Returns:
the result of scanning/**
     * {@inheritDoc}
     *
     * @implSpec This implementation scans the enclosed elements.
     *
     * @param e  {@inheritDoc}
     * @param p  {@inheritDoc}
     * @return the result of scanning
     */
    public R visitPackage(PackageElement e, P p) {
        return scan(e.getEnclosedElements(), p);
    }

    
{@inheritDoc}
Params:
e –  {@inheritDoc}
p –  {@inheritDoc}
Implementation Requirements:
This implementation scans the enclosed elements.
Returns:
the result of scanning/**
     * {@inheritDoc}
     *
     * @implSpec This implementation scans the enclosed elements.
     *
     * @param e  {@inheritDoc}
     * @param p  {@inheritDoc}
     * @return the result of scanning
     */
    public R visitType(TypeElement e, P p) {
        return scan(e.getEnclosedElements(), p);
    }

    
{@inheritDoc}
Params:
e –  {@inheritDoc}
p –  {@inheritDoc}
Implementation Requirements:
This implementation scans the enclosed elements, unless the element is a RESOURCE_VARIABLE in which case 
visitUnknown is called.
Returns:
the result of scanning/**
     * {@inheritDoc}
     *
     * @implSpec This implementation scans the enclosed elements, unless the
     * element is a {@code RESOURCE_VARIABLE} in which case {@code
     * visitUnknown} is called.
     *
     * @param e  {@inheritDoc}
     * @param p  {@inheritDoc}
     * @return the result of scanning
     */
    public R visitVariable(VariableElement e, P p) {
        if (e.getKind() != ElementKind.RESOURCE_VARIABLE)
            return scan(e.getEnclosedElements(), p);
        else
            return visitUnknown(e, p);
    }

    
{@inheritDoc}
Params:
e –  {@inheritDoc}
p –  {@inheritDoc}
Implementation Requirements:
This implementation scans the parameters.
Returns:
the result of scanning/**
     * {@inheritDoc}
     *
     * @implSpec This implementation scans the parameters.
     *
     * @param e  {@inheritDoc}
     * @param p  {@inheritDoc}
     * @return the result of scanning
     */
    public R visitExecutable(ExecutableElement e, P p) {
        return scan(e.getParameters(), p);
    }

    
{@inheritDoc}
Params:
e –  {@inheritDoc}
p –  {@inheritDoc}
Implementation Requirements:
This implementation scans the enclosed elements.
Returns:
the result of scanning/**
     * {@inheritDoc}
     *
     * @implSpec This implementation scans the enclosed elements.
     *
     * @param e  {@inheritDoc}
     * @param p  {@inheritDoc}
     * @return the result of scanning
     */
    public R visitTypeParameter(TypeParameterElement e, P p) {
        return scan(e.getEnclosedElements(), p);
    }
}