The ElementFilter.java Java example source code
/*
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* 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.
*
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package javax.lang.model.util;
import java.util.Collections;
import java.util.List;
import java.util.Set;
import java.util.EnumSet;
import java.util.ArrayList;
import java.util.LinkedHashSet;
import javax.lang.model.element.*;
/**
* Filters for selecting just the elements of interest from a
* collection of elements. The returned sets and lists are new
* collections and do use the argument as a backing store. The
* methods in this class do not make any attempts to guard against
* concurrent modifications of the arguments. The returned sets and
* lists are mutable but unsafe for concurrent access. A returned set
* has the same iteration order as the argument set to a method.
*
* <p>If iterables and sets containing {@code null} are passed as
* arguments to methods in this class, a {@code NullPointerException}
* will be thrown.
*
* <p>Note that a static import statement can make the text of
* calls to the methods in this class more concise; for example:
*
* <blockquote> * import static javax.lang.model.util.ElementFilter.*;
* ...
* {@code List<VariableElement>} fs = fieldsIn(someClass.getEnclosedElements());
* </pre>
*
* @author Joseph D. Darcy
* @author Scott Seligman
* @author Peter von der Ahé
* @author Martin Buchholz
* @since 1.6
*/
public class ElementFilter {
private ElementFilter() {} // Do not instantiate.
private static final Set<ElementKind> CONSTRUCTOR_KIND =
Collections.unmodifiableSet(EnumSet.of(ElementKind.CONSTRUCTOR));
private static final Set<ElementKind> FIELD_KINDS =
Collections.unmodifiableSet(EnumSet.of(ElementKind.FIELD,
ElementKind.ENUM_CONSTANT));
private static final Set<ElementKind> METHOD_KIND =
Collections.unmodifiableSet(EnumSet.of(ElementKind.METHOD));
private static final Set<ElementKind> PACKAGE_KIND =
Collections.unmodifiableSet(EnumSet.of(ElementKind.PACKAGE));
private static final Set<ElementKind> TYPE_KINDS =
Collections.unmodifiableSet(EnumSet.of(ElementKind.CLASS,
ElementKind.ENUM,
ElementKind.INTERFACE,
ElementKind.ANNOTATION_TYPE));
/**
* Returns a list of fields in {@code elements}.
* @return a list of fields in {@code elements}
* @param elements the elements to filter
*/
public static List<VariableElement>
fieldsIn(Iterable<? extends Element> elements) {
return listFilter(elements, FIELD_KINDS, VariableElement.class);
}
/**
* Returns a set of fields in {@code elements}.
* @return a set of fields in {@code elements}
* @param elements the elements to filter
*/
public static Set<VariableElement>
fieldsIn(Set<? extends Element> elements) {
return setFilter(elements, FIELD_KINDS, VariableElement.class);
}
/**
* Returns a list of constructors in {@code elements}.
* @return a list of constructors in {@code elements}
* @param elements the elements to filter
*/
public static List<ExecutableElement>
constructorsIn(Iterable<? extends Element> elements) {
return listFilter(elements, CONSTRUCTOR_KIND, ExecutableElement.class);
}
/**
* Returns a set of constructors in {@code elements}.
* @return a set of constructors in {@code elements}
* @param elements the elements to filter
*/
public static Set<ExecutableElement>
constructorsIn(Set<? extends Element> elements) {
return setFilter(elements, CONSTRUCTOR_KIND, ExecutableElement.class);
}
/**
* Returns a list of methods in {@code elements}.
* @return a list of methods in {@code elements}
* @param elements the elements to filter
*/
public static List<ExecutableElement>
methodsIn(Iterable<? extends Element> elements) {
return listFilter(elements, METHOD_KIND, ExecutableElement.class);
}
/**
* Returns a set of methods in {@code elements}.
* @return a set of methods in {@code elements}
* @param elements the elements to filter
*/
public static Set<ExecutableElement>
methodsIn(Set<? extends Element> elements) {
return setFilter(elements, METHOD_KIND, ExecutableElement.class);
}
/**
* Returns a list of types in {@code elements}.
* @return a list of types in {@code elements}
* @param elements the elements to filter
*/
public static List<TypeElement>
typesIn(Iterable<? extends Element> elements) {
return listFilter(elements, TYPE_KINDS, TypeElement.class);
}
/**
* Returns a set of types in {@code elements}.
* @return a set of types in {@code elements}
* @param elements the elements to filter
*/
public static Set<TypeElement>
typesIn(Set<? extends Element> elements) {
return setFilter(elements, TYPE_KINDS, TypeElement.class);
}
/**
* Returns a list of packages in {@code elements}.
* @return a list of packages in {@code elements}
* @param elements the elements to filter
*/
public static List<PackageElement>
packagesIn(Iterable<? extends Element> elements) {
return listFilter(elements, PACKAGE_KIND, PackageElement.class);
}
/**
* Returns a set of packages in {@code elements}.
* @return a set of packages in {@code elements}
* @param elements the elements to filter
*/
public static Set<PackageElement>
packagesIn(Set<? extends Element> elements) {
return setFilter(elements, PACKAGE_KIND, PackageElement.class);
}
// Assumes targetKinds and E are sensible.
private static <E extends Element> List listFilter(Iterable elements,
Set<ElementKind> targetKinds,
Class<E> clazz) {
List<E> list = new ArrayList();
for (Element e : elements) {
if (targetKinds.contains(e.getKind()))
list.add(clazz.cast(e));
}
return list;
}
// Assumes targetKinds and E are sensible.
private static <E extends Element> Set setFilter(Set elements,
Set<ElementKind> targetKinds,
Class<E> clazz) {
// Return set preserving iteration order of input set.
Set<E> set = new LinkedHashSet();
for (Element e : elements) {
if (targetKinds.contains(e.getKind()))
set.add(clazz.cast(e));
}
return set;
}
}
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