/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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
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 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
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package org.apache.commons.collections4.queue;

import java.util.Queue;

import org.apache.commons.collections4.collection.SynchronizedCollection;

Decorates another Queue to synchronize its behaviour for a multi-threaded environment.

Methods are synchronized, then forwarded to the decorated queue. Iterators must be separately synchronized around the loop.

Type parameters:
  • <E> – the type of the elements in the collection
Since:4.2
/** * Decorates another {@link Queue} to synchronize its behaviour for a multi-threaded environment. * <p> * Methods are synchronized, then forwarded to the decorated queue. Iterators must be separately synchronized around the * loop. * * @param <E> the type of the elements in the collection * @since 4.2 */
public class SynchronizedQueue<E> extends SynchronizedCollection<E> implements Queue<E> {
Serialization version
/** Serialization version */
private static final long serialVersionUID = 1L;
Factory method to create a synchronized queue.
Params:
  • queue – the queue to decorate, must not be null
Type parameters:
  • <E> – the type of the elements in the queue
Throws:
Returns:a new synchronized Queue
/** * Factory method to create a synchronized queue. * * @param <E> * the type of the elements in the queue * @param queue * the queue to decorate, must not be null * @return a new synchronized Queue * @throws NullPointerException * if queue is null */
public static <E> SynchronizedQueue<E> synchronizedQueue(final Queue<E> queue) { return new SynchronizedQueue<>(queue); } // -----------------------------------------------------------------------
Constructor that wraps (not copies).
Params:
  • queue – the queue to decorate, must not be null
Throws:
/** * Constructor that wraps (not copies). * * @param queue * the queue to decorate, must not be null * @throws NullPointerException * if queue is null */
protected SynchronizedQueue(final Queue<E> queue) { super(queue); }
Constructor that wraps (not copies).
Params:
  • queue – the queue to decorate, must not be null
  • lock – the lock to use, must not be null
Throws:
/** * Constructor that wraps (not copies). * * @param queue * the queue to decorate, must not be null * @param lock * the lock to use, must not be null * @throws NullPointerException * if queue or lock is null */
protected SynchronizedQueue(final Queue<E> queue, final Object lock) { super(queue, lock); }
Gets the queue being decorated.
Returns:the decorated queue
/** * Gets the queue being decorated. * * @return the decorated queue */
@Override protected Queue<E> decorated() { return (Queue<E>) super.decorated(); } @Override public E element() { synchronized (lock) { return decorated().element(); } } @Override public boolean equals(final Object object) { if (object == this) { return true; } synchronized (lock) { return decorated().equals(object); } } // ----------------------------------------------------------------------- @Override public int hashCode() { synchronized (lock) { return decorated().hashCode(); } } @Override public boolean offer(final E e) { synchronized (lock) { return decorated().offer(e); } } @Override public E peek() { synchronized (lock) { return decorated().peek(); } } @Override public E poll() { synchronized (lock) { return decorated().poll(); } } @Override public E remove() { synchronized (lock) { return decorated().remove(); } } }