    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}