synchronizedsortedbag.java

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/*
 *  Copyright 2003-2004 The Apache Software Foundation
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.apache.commons.collections.bag;

import java.util.Comparator;

import org.apache.commons.collections.Bag;
import org.apache.commons.collections.SortedBag;

/**
 * Decorates another <code>SortedBag</code> to synchronize its behaviour
 * for a multi-threaded environment.
 * <p>
 * Methods are synchronized, then forwarded to the decorated bag.
 * Iterators must be separately synchronized around the loop.
 * <p>
 * This class is Serializable from Commons Collections 3.1.
 *
 * @since Commons Collections 3.0
 * @version $Revision: 155406 $ $Date: 2005-02-26 12:55:26 +0000 (Sat, 26 Feb 2005) $
 * 
 * @author Stephen Colebourne
 */
public class SynchronizedSortedBag
        extends SynchronizedBag implements SortedBag {

    /** Serialization version */
    private static final long serialVersionUID = 722374056718497858L;

    /**
     * Factory method to create a synchronized sorted bag.
     * 
     * @param bag  the bag to decorate, must not be null
     * @return a new synchronized SortedBag
     * @throws IllegalArgumentException if bag is null
     */
    public static SortedBag decorate(SortedBag bag) {
        return new SynchronizedSortedBag(bag);
    }
    
    //-----------------------------------------------------------------------
    /**
     * Constructor that wraps (not copies).
     * 
     * @param bag  the bag to decorate, must not be null
     * @throws IllegalArgumentException if bag is null
     */
    protected SynchronizedSortedBag(SortedBag bag) {
        super(bag);
    }

    /**
     * Constructor that wraps (not copies).
     * 
     * @param bag  the bag to decorate, must not be null
     * @param lock  the lock to use, must not be null
     * @throws IllegalArgumentException if bag is null
     */
    protected SynchronizedSortedBag(Bag bag, Object lock) {
        super(bag, lock);
    }

    /**
     * Gets the bag being decorated.
     * 
     * @return the decorated bag
     */
    protected SortedBag getSortedBag() {
        return (SortedBag) collection;
    }
    
    //-----------------------------------------------------------------------
    public synchronized Object first() {
        synchronized (lock) {
            return getSortedBag().first();
        }
    }

    public synchronized Object last() {
        synchronized (lock) {
            return getSortedBag().last();
        }
    }

    public synchronized Comparator comparator() {
        synchronized (lock) {
            return getSortedBag().comparator();
        }
    }

}