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 * <p>
032 * This class is Serializable from Commons Collections 3.1.
033 * </p>
034 *
035 * @param <E> the type of elements in this bag
036 * @since 3.0
037 */
038public class SynchronizedSortedBag<E> extends SynchronizedBag<E> implements SortedBag<E> {
039
040    /** Serialization version */
041    private static final long serialVersionUID = 722374056718497858L;
042
043    /**
044     * Factory method to create a synchronized sorted bag.
045     *
046     * @param <E> the type of the elements in the bag
047     * @param bag  the bag to decorate, must not be null
048     * @return a new synchronized SortedBag
049     * @throws NullPointerException if bag is null
050     * @since 4.0
051     */
052    public static <E> SynchronizedSortedBag<E> synchronizedSortedBag(final SortedBag<E> bag) {
053        return new SynchronizedSortedBag<>(bag);
054    }
055
056    //-----------------------------------------------------------------------
057    /**
058     * Constructor that wraps (not copies).
059     *
060     * @param bag  the bag to decorate, must not be null
061     * @throws NullPointerException if bag is null
062     */
063    protected SynchronizedSortedBag(final SortedBag<E> bag) {
064        super(bag);
065    }
066
067    /**
068     * Constructor that wraps (not copies).
069     *
070     * @param bag  the bag to decorate, must not be null
071     * @param lock  the lock to use, must not be null
072     * @throws NullPointerException if bag or lock is null
073     */
074    protected SynchronizedSortedBag(final Bag<E> bag, final Object lock) {
075        super(bag, lock);
076    }
077
078    /**
079     * Gets the bag being decorated.
080     *
081     * @return the decorated bag
082     */
083    protected SortedBag<E> getSortedBag() {
084        return (SortedBag<E>) decorated();
085    }
086
087    //-----------------------------------------------------------------------
088
089    @Override
090    public synchronized E first() {
091        synchronized (lock) {
092            return getSortedBag().first();
093        }
094    }
095
096    @Override
097    public synchronized E last() {
098        synchronized (lock) {
099            return getSortedBag().last();
100        }
101    }
102
103    @Override
104    public synchronized Comparator<? super E> comparator() {
105        synchronized (lock) {
106            return getSortedBag().comparator();
107        }
108    }
109
110}