gt:     Set<E> set = new LinkedHashSet<E>();
context: /*
   * Copyright (c) 2005, 2006, 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.lang.Iterable;
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Set;
  import java.util.EnumSet;
  import java.util.ArrayList;
  import java.util.LinkedHashSet;
  import java.util.NoSuchElementException;
  
  import javax.lang.model.element.*;
  import javax.lang.model.type.*;
  
  /**
   * 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 <i>static import</i> statement can make the text of calls to the
   * methods in this class more concise; for example:
   * 
   * <blockquote>
   * 
   * <pre>
   *     import static javax.lang.model.util.ElementFilter.*;
   *     ...
   *         {@code List<VariableElement>} fs = fieldsIn(someClass.getEnclosedElements());
   * </pre>
   * 
   * </blockquote>
   * 
   * @author Joseph D. Darcy
   * @author Scott Seligman
   * @author Peter von der Ah&eacute;
   * @author Martin Buchholz
   * @since 1.6
   */
  public class ElementFilter {
    private ElementFilter() {
    } // Do not instantiate.
  
    private static Set<ElementKind> CONSTRUCTOR_KIND = Collections
        .unmodifiableSet(EnumSet.of(ElementKind.CONSTRUCTOR));
  
    private static Set<ElementKind> FIELD_KINDS = Collections
        .unmodifiableSet(EnumSet.of(ElementKind.FIELD, ElementKind.ENUM_CONSTANT));
    private static Set<ElementKind> METHOD_KIND = Collections
        .unmodifiableSet(EnumSet.of(ElementKind.METHOD));
  
    private static Set<ElementKind> PACKAGE_KIND = Collections
        .unmodifiableSet(EnumSet.of(ElementKind.PACKAGE));
  
    private static 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<E> listFilter(
        Iterable<? extends Element> elements, Set<ElementKind> targetKinds,
        Class<E> clazz) {
      List<E> list = new ArrayList<E>();
      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.
  