LinkedSet.java

/*
 * Copyright (c) 2008, Harald Kuhr
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * 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.
 *     * Neither the name "TwelveMonkeys" nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS 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 COPYRIGHT OWNER OR
 * 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.
 */

package com.twelvemonkeys.util;

import java.util.*;
import java.io.Serializable;

/**
 * Generic map and linked list implementation of the {@code Set} interface,
 * with predictable iteration order.
 * <p>
 * Resembles {@code LinkedHashSet} from JDK 1.4+, but is backed by a generic
 * {@code LinkedMap}, rather than implementing a particular algoritm.
 * <p/>
 * @see LinkedMap
 *
 * @author <a href="mailto:harald.kuhr@gmail.com">Harald Kuhr</a>
 * @version $Id: //depot/branches/personal/haraldk/twelvemonkeys/release-2/twelvemonkeys-core/src/main/java/com/twelvemonkeys/util/LinkedSet.java#1 $
 */
public class LinkedSet<E> extends AbstractSet<E> implements Set<E>, Cloneable, Serializable {

    private final static Object DUMMY = new Object();

    private final Map<E, Object> map;

    public LinkedSet() {
        map = new LinkedMap<E, Object>();
    }

    public LinkedSet(Collection<E> pCollection) {
        this();
        addAll(pCollection);
    }

    public boolean addAll(Collection<? extends E> pCollection) {
        boolean changed = false;
        for (E value : pCollection) {
            if (add(value) && !changed) {
                changed = true;
            }
        }
        return changed;
    }

    public boolean add(E pValue) {
        return map.put(pValue, DUMMY) == null;
    }

    public int size() {
        return map.size();
    }

    public Iterator<E> iterator() {
        return map.keySet().iterator();
    }
}