001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.collections4.bag;
018
019import java.util.Comparator;
020
021import org.apache.commons.collections4.Bag;
022import org.apache.commons.collections4.SortedBag;
023
024/**
025 * Decorates another {@link SortedBag} to synchronize its behaviour
026 * for a multi-threaded environment.
027 * <p>
028 * Methods are synchronized, then forwarded to the decorated bag.
029 * Iterators must be separately synchronized around the loop.
030 * <p>
031 * This class is Serializable from Commons Collections 3.1.
032 *
033 * @param <E> the type of elements in this bag
034 * @since 3.0
035 */
036public class SynchronizedSortedBag<E> extends SynchronizedBag<E> implements SortedBag<E> {
037
038    /** Serialization version */
039    private static final long serialVersionUID = 722374056718497858L;
040
041    /**
042     * Factory method to create a synchronized sorted bag.
043     *
044     * @param <E> the type of the elements in the bag
045     * @param bag  the bag to decorate, must not be null
046     * @return a new synchronized SortedBag
047     * @throws NullPointerException if bag is null
048     * @since 4.0
049     */
050    public static <E> SynchronizedSortedBag<E> synchronizedSortedBag(final SortedBag<E> bag) {
051        return new SynchronizedSortedBag<>(bag);
052    }
053
054    //-----------------------------------------------------------------------
055    /**
056     * Constructor that wraps (not copies).
057     *
058     * @param bag  the bag to decorate, must not be null
059     * @throws NullPointerException if bag is null
060     */
061    protected SynchronizedSortedBag(final SortedBag<E> bag) {
062        super(bag);
063    }
064
065    /**
066     * Constructor that wraps (not copies).
067     *
068     * @param bag  the bag to decorate, must not be null
069     * @param lock  the lock to use, must not be null
070     * @throws NullPointerException if bag or lock is null
071     */
072    protected SynchronizedSortedBag(final Bag<E> bag, final Object lock) {
073        super(bag, lock);
074    }
075
076    /**
077     * Gets the bag being decorated.
078     *
079     * @return the decorated bag
080     */
081    protected SortedBag<E> getSortedBag() {
082        return (SortedBag<E>) decorated();
083    }
084
085    //-----------------------------------------------------------------------
086
087    @Override
088    public synchronized E first() {
089        synchronized (lock) {
090            return getSortedBag().first();
091        }
092    }
093
094    @Override
095    public synchronized E last() {
096        synchronized (lock) {
097            return getSortedBag().last();
098        }
099    }
100
101    @Override
102    public synchronized Comparator<? super E> comparator() {
103        synchronized (lock) {
104            return getSortedBag().comparator();
105        }
106    }
107
108}