Java tutorial
/* * Copyright (c) 2005, 2017, 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 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.*; import javax.lang.model.element.ModuleElement.Directive; import javax.lang.model.element.ModuleElement.DirectiveKind; import javax.lang.model.element.ModuleElement.ExportsDirective; import javax.lang.model.element.ModuleElement.OpensDirective; import javax.lang.model.element.ModuleElement.ProvidesDirective; import javax.lang.model.element.ModuleElement.RequiresDirective; import javax.lang.model.element.ModuleElement.UsesDirective; /** * 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. * * @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> MODULE_KIND = Collections.unmodifiableSet(EnumSet.of(ElementKind.MODULE)); 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); } /** * Returns a list of modules in {@code elements}. * @return a list of modules in {@code elements} * @param elements the elements to filter * @since 9 * @spec JPMS */ public static List<ModuleElement> modulesIn(Iterable<? extends Element> elements) { return listFilter(elements, MODULE_KIND, ModuleElement.class); } /** * Returns a set of modules in {@code elements}. * @return a set of modules in {@code elements} * @param elements the elements to filter * @since 9 * @spec JPMS */ public static Set<ModuleElement> modulesIn(Set<? extends Element> elements) { return setFilter(elements, MODULE_KIND, ModuleElement.class); } // Assumes targetKinds and E are sensible. private static <E extends Element> List<E> listFilter(Iterable<? extends Element> 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<E> setFilter(Set<? extends Element> 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; } /** * Returns a list of {@code exports} directives in {@code directives}. * @return a list of {@code exports} directives in {@code directives} * @param directives the directives to filter * @since 9 * @spec JPMS */ public static List<ExportsDirective> exportsIn(Iterable<? extends Directive> directives) { return listFilter(directives, DirectiveKind.EXPORTS, ExportsDirective.class); } /** * Returns a list of {@code opens} directives in {@code directives}. * @return a list of {@code opens} directives in {@code directives} * @param directives the directives to filter * @since 9 */ public static List<OpensDirective> opensIn(Iterable<? extends Directive> directives) { return listFilter(directives, DirectiveKind.OPENS, OpensDirective.class); } /** * Returns a list of {@code provides} directives in {@code directives}. * @return a list of {@code provides} directives in {@code directives} * @param directives the directives to filter * @since 9 * @spec JPMS */ public static List<ProvidesDirective> providesIn(Iterable<? extends Directive> directives) { return listFilter(directives, DirectiveKind.PROVIDES, ProvidesDirective.class); } /** * Returns a list of {@code requires} directives in {@code directives}. * @return a list of {@code requires} directives in {@code directives} * @param directives the directives to filter * @since 9 * @spec JPMS */ public static List<RequiresDirective> requiresIn(Iterable<? extends Directive> directives) { return listFilter(directives, DirectiveKind.REQUIRES, RequiresDirective.class); } /** * Returns a list of {@code uses} directives in {@code directives}. * @return a list of {@code uses} directives in {@code directives} * @param directives the directives to filter * @since 9 * @spec JPMS */ public static List<UsesDirective> usesIn(Iterable<? extends Directive> directives) { return listFilter(directives, DirectiveKind.USES, UsesDirective.class); } // Assumes directiveKind and D are sensible. private static <D extends Directive> List<D> listFilter(Iterable<? extends Directive> directives, DirectiveKind directiveKind, Class<D> clazz) { List<D> list = new ArrayList<>(); for (Directive d : directives) { if (d.getKind() == directiveKind) list.add(clazz.cast(d)); } return list; } }