javax.lang.model.util.ElementScanner6 Maven / Gradle / Ivy
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*
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* published by the Free Software Foundation. Oracle designates this
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* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
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* 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).
*
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* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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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 {@link SourceVersion#RELEASE_6 RELEASE_6}
* source version. The 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
* 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.
*
* 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 {@code 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 {@link java.lang.Override @Override} will help
* ensure that methods are overridden as intended.
*
*
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"}.
*
*
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 the return type of this visitor's methods. Use {@link
* Void} for visitors that do not need to return results.
* @param 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
*
* @see ElementScanner7
* @see ElementScanner8
* @see ElementScanner9
* @since 1.6
*/
@SupportedSourceVersion(RELEASE_6)
public class ElementScanner6 extends AbstractElementVisitor6 {
/**
* The specified default value.
*/
protected final R DEFAULT_VALUE;
/**
* 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
protected ElementScanner6(){
DEFAULT_VALUE = null;
}
/**
* 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
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 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.
*
* @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 {@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} 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} 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}
*
* 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} 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} 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);
}
}