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From scolebou...@apache.org
Subject cvs commit: jakarta-commons/collections/src/java/org/apache/commons/collections/decorators SequencedSet.java
Date Sat, 10 May 2003 15:10:22 GMT
scolebourne    2003/05/10 08:10:22

  Added:       collections/src/java/org/apache/commons/collections/decorators
                        SequencedSet.java
  Log:
  Add sequenced decorator
  
  Revision  Changes    Path
  1.1                  jakarta-commons/collections/src/java/org/apache/commons/collections/decorators/SequencedSet.java
  
  Index: SequencedSet.java
  ===================================================================
  /*
   * $Header: /home/cvs/jakarta-commons/collections/src/java/org/apache/commons/collections/decorators/SequencedSet.java,v
1.1 2003/05/10 15:10:22 scolebourne Exp $
   * ====================================================================
   *
   * The Apache Software License, Version 1.1
   *
   * Copyright (c) 2003 The Apache Software Foundation.  All rights
   * reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in
   *    the documentation and/or other materials provided with the
   *    distribution.
   *
   * 3. The end-user documentation included with the redistribution, if
   *    any, must include the following acknowledgment:
   *       "This product includes software developed by the
   *        Apache Software Foundation (http://www.apache.org/)."
   *    Alternately, this acknowledgment may appear in the software itself,
   *    if and wherever such third-party acknowledgments normally appear.
   *
   * 4. The names "The Jakarta Project", "Commons", and "Apache Software
   *    Foundation" must not be used to endorse or promote products derived
   *    from this software without prior written permission. For written
   *    permission, please contact apache@apache.org.
   *
   * 5. Products derived from this software may not be called "Apache"
   *    nor may "Apache" appear in their names without prior written
   *    permission of the Apache Software Foundation.
   *
   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  package org.apache.commons.collections.decorators;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Set;
  
  /**
   * <code>SequencedSet</code> decorates another <code>Set</code>
   * to ensure that the order of addition is retained and used by the iterator.
   * <p>
   * If an object is added to the Set for a second time, it will remain in the
   * original position in the iteration.
   * <p>
   * The order can be observed via the iterator or toArray methods.
   *
   * @since Commons Collections 3.0
   * @version $Revision: 1.1 $ $Date: 2003/05/10 15:10:22 $
   * 
   * @author Stephen Colebourne
   * @author Henning P. Schmiedehausen
   */
  public class SequencedSet extends AbstractSetDecorator implements Set {
  
      /** Internal list to hold the sequence of objects */
      protected final List setOrder = new ArrayList();
  
      /**
       * Factory method to create an unmodifiable set.
       * 
       * @param set  the set to decorate, must not be null
       * @throws IllegalArgumentException if set is null
       */
      public static Set decorate(Set set) {
          return new SequencedSet(set);
      }
  
      /**
       * Constructor that wraps (not copies).
       * 
       * @param set  the set to decorate, must not be null
       * @throws IllegalArgumentException if set is null
       */
      protected SequencedSet(Set set) {
          super(set);
          setOrder.addAll(set);
      }
  
      //-----------------------------------------------------------------------
      public void clear() {
          collection.clear();
          setOrder.clear();
      }
  
      public Iterator iterator() {
          return new SequencedSetIterator(setOrder.iterator(), collection);
      }
  
      public boolean add(Object object) {
          if (collection.contains(object)) {
              // re-adding doesn't change order
              return collection.add(object);
          } else {
              // first add, so add to both set and list
              boolean result = collection.add(object);
              setOrder.add(object);
              return result;
          }
      }
  
      public boolean addAll(Collection coll) {
          boolean result = false;
          for (Iterator it = coll.iterator(); it.hasNext();) {
              Object object = it.next();
              result = result | add(object);
          }
          return result;
      }
  
      public boolean remove(Object object) {
          boolean result = collection.remove(object);
          setOrder.remove(object);
          return result;
      }
  
      public boolean removeAll(Collection coll) {
          boolean result = false;
          for (Iterator it = coll.iterator(); it.hasNext();) {
              Object object = it.next();
              result = result | remove(object);
          }
          return result;
      }
  
      public boolean retainAll(Collection coll) {
          boolean result = collection.retainAll(coll);
          if (result == false) {
              return false;
          } else if (collection.size() == 0) {
              setOrder.clear();
          } else {
              for (Iterator it = setOrder.iterator(); it.hasNext();) {
                  Object object = (Object) it.next();
                  if (collection.contains(object) == false) {
                      it.remove();
                  }
              }
          }
          return result;
      }
  
      public Object[] toArray() {
          return setOrder.toArray();
      }
  
      public Object[] toArray(Object a[]) {
          return setOrder.toArray(a);
      }
  
      /**
       * Internal iterator handle remove.
       */
      protected static class SequencedSetIterator extends AbstractIteratorDecorator {
          
          /** Object we iterate on */
          protected final Collection set;
          /** Last object retrieved */
          protected Object last;
  
          private SequencedSetIterator(Iterator iterator, Collection set) {
              super(iterator);
              this.set = set;
          }
  
          public Object next() {
              last = iterator.next();
              return last;
          }
  
          public void remove() {
              set.remove(last);
              iterator.remove();
              last = null;
          }
      }
  
  }
  
  
  

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