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/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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/*
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* This file is available under and governed by the GNU General Public
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* License version 2 only, as published by the Free Software Foundation.
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* However, the following notice accompanied the original version of this
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* file:
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*
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* Written by Doug Lea with assistance from members of JCP JSR-166
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* Expert Group and released to the public domain, as explained at
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* http://creativecommons.org/publicdomain/zero/1.0/
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*/
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package java.util.concurrent;
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import java.util.concurrent.atomic.AtomicInteger;
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import java.util.concurrent.locks.Condition;
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import java.util.concurrent.locks.ReentrantLock;
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import java.util.AbstractQueue;
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import java.util.Collection;
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import java.util.Iterator;
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import java.util.NoSuchElementException;
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/**
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* An optionally-bounded {@linkplain BlockingQueue blocking queue} based on
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* linked nodes.
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* This queue orders elements FIFO (first-in-first-out).
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* The <em>head</em> of the queue is that element that has been on the
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* queue the longest time.
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* The <em>tail</em> of the queue is that element that has been on the
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* queue the shortest time. New elements
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* are inserted at the tail of the queue, and the queue retrieval
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* operations obtain elements at the head of the queue.
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* Linked queues typically have higher throughput than array-based queues but
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* less predictable performance in most concurrent applications.
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*
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* <p> The optional capacity bound constructor argument serves as a
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* way to prevent excessive queue expansion. The capacity, if unspecified,
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* is equal to {@link Integer#MAX_VALUE}. Linked nodes are
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* dynamically created upon each insertion unless this would bring the
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* queue above capacity.
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*
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* <p>This class and its iterator implement all of the
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* <em>optional</em> methods of the {@link Collection} and {@link
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* Iterator} interfaces.
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*
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* <p>This class is a member of the
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* <a href="{@docRoot}/../technotes/guides/collections/index.html">
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* Java Collections Framework</a>.
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*
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* @since 1.5
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* @author Doug Lea
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* @param <E> the type of elements held in this collection
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*
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*/
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public class LinkedBlockingQueue<E> extends AbstractQueue<E>
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implements BlockingQueue<E>, java.io.Serializable {
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private static final long serialVersionUID = -6903933977591709194L;
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/*
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* A variant of the "two lock queue" algorithm. The putLock gates
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* entry to put (and offer), and has an associated condition for
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* waiting puts. Similarly for the takeLock. The "count" field
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* that they both rely on is maintained as an atomic to avoid
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* needing to get both locks in most cases. Also, to minimize need
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* for puts to get takeLock and vice-versa, cascading notifies are
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* used. When a put notices that it has enabled at least one take,
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* it signals taker. That taker in turn signals others if more
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* items have been entered since the signal. And symmetrically for
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* takes signalling puts. Operations such as remove(Object) and
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* iterators acquire both locks.
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*
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* Visibility between writers and readers is provided as follows:
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*
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* Whenever an element is enqueued, the putLock is acquired and
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* count updated. A subsequent reader guarantees visibility to the
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* enqueued Node by either acquiring the putLock (via fullyLock)
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* or by acquiring the takeLock, and then reading n = count.get();
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* this gives visibility to the first n items.
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*
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* To implement weakly consistent iterators, it appears we need to
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* keep all Nodes GC-reachable from a predecessor dequeued Node.
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* That would cause two problems:
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* - allow a rogue Iterator to cause unbounded memory retention
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* - cause cross-generational linking of old Nodes to new Nodes if
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* a Node was tenured while live, which generational GCs have a
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* hard time dealing with, causing repeated major collections.
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* However, only non-deleted Nodes need to be reachable from
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* dequeued Nodes, and reachability does not necessarily have to
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* be of the kind understood by the GC. We use the trick of
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* linking a Node that has just been dequeued to itself. Such a
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* self-link implicitly means to advance to head.next.
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*/
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/**
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* Linked list node class
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*/
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static class Node<E> {
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E item;
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/**
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* One of:
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* - the real successor Node
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* - this Node, meaning the successor is head.next
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* - null, meaning there is no successor (this is the last node)
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*/
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Node<E> next;
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Node(E x) { item = x; }
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}
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/** The capacity bound, or Integer.MAX_VALUE if none */
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private final int capacity;
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/** Current number of elements */
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private final AtomicInteger count = new AtomicInteger(0);
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/**
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* Head of linked list.
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* Invariant: head.item == null
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*/
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private transient Node<E> head;
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/**
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* Tail of linked list.
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* Invariant: last.next == null
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*/
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private transient Node<E> last;
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/** Lock held by take, poll, etc */
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private final ReentrantLock takeLock = new ReentrantLock();
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/** Wait queue for waiting takes */
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private final Condition notEmpty = takeLock.newCondition();
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/** Lock held by put, offer, etc */
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private final ReentrantLock putLock = new ReentrantLock();
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/** Wait queue for waiting puts */
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private final Condition notFull = putLock.newCondition();
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/**
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* Signals a waiting take. Called only from put/offer (which do not
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* otherwise ordinarily lock takeLock.)
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*/
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private void signalNotEmpty() {
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final ReentrantLock takeLock = this.takeLock;
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takeLock.lock();
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try {
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notEmpty.signal();
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} finally {
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takeLock.unlock();
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}
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}
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/**
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* Signals a waiting put. Called only from take/poll.
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*/
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private void signalNotFull() {
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final ReentrantLock putLock = this.putLock;
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putLock.lock();
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try {
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notFull.signal();
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} finally {
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putLock.unlock();
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}
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}
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/**
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* Links node at end of queue.
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*
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* @param node the node
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*/
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private void enqueue(Node<E> node) {
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// assert putLock.isHeldByCurrentThread();
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// assert last.next == null;
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last = last.next = node;
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}
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/**
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* Removes a node from head of queue.
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*
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* @return the node
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*/
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private E dequeue() {
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// assert takeLock.isHeldByCurrentThread();
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// assert head.item == null;
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Node<E> h = head;
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Node<E> first = h.next;
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h.next = h; // help GC
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head = first;
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E x = first.item;
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first.item = null;
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return x;
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}
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/**
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* Lock to prevent both puts and takes.
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*/
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void fullyLock() {
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putLock.lock();
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takeLock.lock();
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}
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/**
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* Unlock to allow both puts and takes.
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*/
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void fullyUnlock() {
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takeLock.unlock();
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putLock.unlock();
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}
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// /**
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// * Tells whether both locks are held by current thread.
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// */
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// boolean isFullyLocked() {
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// return (putLock.isHeldByCurrentThread() &&
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// takeLock.isHeldByCurrentThread());
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// }
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/**
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* Creates a {@code LinkedBlockingQueue} with a capacity of
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* {@link Integer#MAX_VALUE}.
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*/
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public LinkedBlockingQueue() {
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this(Integer.MAX_VALUE);
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}
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/**
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* Creates a {@code LinkedBlockingQueue} with the given (fixed) capacity.
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*
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* @param capacity the capacity of this queue
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* @throws IllegalArgumentException if {@code capacity} is not greater
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* than zero
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*/
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public LinkedBlockingQueue(int capacity) {
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if (capacity <= 0) throw new IllegalArgumentException();
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this.capacity = capacity;
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last = head = new Node<E>(null);
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}
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/**
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* Creates a {@code LinkedBlockingQueue} with a capacity of
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* {@link Integer#MAX_VALUE}, initially containing the elements of the
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* given collection,
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* added in traversal order of the collection's iterator.
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*
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* @param c the collection of elements to initially contain
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* @throws NullPointerException if the specified collection or any
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* of its elements are null
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*/
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public LinkedBlockingQueue(Collection<? extends E> c) {
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this(Integer.MAX_VALUE);
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final ReentrantLock putLock = this.putLock;
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putLock.lock(); // Never contended, but necessary for visibility
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try {
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int n = 0;
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for (E e : c) {
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if (e == null)
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throw new NullPointerException();
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if (n == capacity)
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throw new IllegalStateException("Queue full");
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enqueue(new Node<E>(e));
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++n;
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}
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count.set(n);
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} finally {
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putLock.unlock();
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}
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}
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// this doc comment is overridden to remove the reference to collections
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// greater in size than Integer.MAX_VALUE
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/**
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* Returns the number of elements in this queue.
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*
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* @return the number of elements in this queue
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*/
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public int size() {
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return count.get();
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}
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// this doc comment is a modified copy of the inherited doc comment,
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// without the reference to unlimited queues.
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/**
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* Returns the number of additional elements that this queue can ideally
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* (in the absence of memory or resource constraints) accept without
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* blocking. This is always equal to the initial capacity of this queue
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* less the current {@code size} of this queue.
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*
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|
314 |
* <p>Note that you <em>cannot</em> always tell if an attempt to insert
|
jaroslav@1890
|
315 |
* an element will succeed by inspecting {@code remainingCapacity}
|
jaroslav@1890
|
316 |
* because it may be the case that another thread is about to
|
jaroslav@1890
|
317 |
* insert or remove an element.
|
jaroslav@1890
|
318 |
*/
|
jaroslav@1890
|
319 |
public int remainingCapacity() {
|
jaroslav@1890
|
320 |
return capacity - count.get();
|
jaroslav@1890
|
321 |
}
|
jaroslav@1890
|
322 |
|
jaroslav@1890
|
323 |
/**
|
jaroslav@1890
|
324 |
* Inserts the specified element at the tail of this queue, waiting if
|
jaroslav@1890
|
325 |
* necessary for space to become available.
|
jaroslav@1890
|
326 |
*
|
jaroslav@1890
|
327 |
* @throws InterruptedException {@inheritDoc}
|
jaroslav@1890
|
328 |
* @throws NullPointerException {@inheritDoc}
|
jaroslav@1890
|
329 |
*/
|
jaroslav@1890
|
330 |
public void put(E e) throws InterruptedException {
|
jaroslav@1890
|
331 |
if (e == null) throw new NullPointerException();
|
jaroslav@1890
|
332 |
// Note: convention in all put/take/etc is to preset local var
|
jaroslav@1890
|
333 |
// holding count negative to indicate failure unless set.
|
jaroslav@1890
|
334 |
int c = -1;
|
jaroslav@1890
|
335 |
Node<E> node = new Node(e);
|
jaroslav@1890
|
336 |
final ReentrantLock putLock = this.putLock;
|
jaroslav@1890
|
337 |
final AtomicInteger count = this.count;
|
jaroslav@1890
|
338 |
putLock.lockInterruptibly();
|
jaroslav@1890
|
339 |
try {
|
jaroslav@1890
|
340 |
/*
|
jaroslav@1890
|
341 |
* Note that count is used in wait guard even though it is
|
jaroslav@1890
|
342 |
* not protected by lock. This works because count can
|
jaroslav@1890
|
343 |
* only decrease at this point (all other puts are shut
|
jaroslav@1890
|
344 |
* out by lock), and we (or some other waiting put) are
|
jaroslav@1890
|
345 |
* signalled if it ever changes from capacity. Similarly
|
jaroslav@1890
|
346 |
* for all other uses of count in other wait guards.
|
jaroslav@1890
|
347 |
*/
|
jaroslav@1890
|
348 |
while (count.get() == capacity) {
|
jaroslav@1890
|
349 |
notFull.await();
|
jaroslav@1890
|
350 |
}
|
jaroslav@1890
|
351 |
enqueue(node);
|
jaroslav@1890
|
352 |
c = count.getAndIncrement();
|
jaroslav@1890
|
353 |
if (c + 1 < capacity)
|
jaroslav@1890
|
354 |
notFull.signal();
|
jaroslav@1890
|
355 |
} finally {
|
jaroslav@1890
|
356 |
putLock.unlock();
|
jaroslav@1890
|
357 |
}
|
jaroslav@1890
|
358 |
if (c == 0)
|
jaroslav@1890
|
359 |
signalNotEmpty();
|
jaroslav@1890
|
360 |
}
|
jaroslav@1890
|
361 |
|
jaroslav@1890
|
362 |
/**
|
jaroslav@1890
|
363 |
* Inserts the specified element at the tail of this queue, waiting if
|
jaroslav@1890
|
364 |
* necessary up to the specified wait time for space to become available.
|
jaroslav@1890
|
365 |
*
|
jaroslav@1890
|
366 |
* @return {@code true} if successful, or {@code false} if
|
jaroslav@1890
|
367 |
* the specified waiting time elapses before space is available.
|
jaroslav@1890
|
368 |
* @throws InterruptedException {@inheritDoc}
|
jaroslav@1890
|
369 |
* @throws NullPointerException {@inheritDoc}
|
jaroslav@1890
|
370 |
*/
|
jaroslav@1890
|
371 |
public boolean offer(E e, long timeout, TimeUnit unit)
|
jaroslav@1890
|
372 |
throws InterruptedException {
|
jaroslav@1890
|
373 |
|
jaroslav@1890
|
374 |
if (e == null) throw new NullPointerException();
|
jaroslav@1890
|
375 |
long nanos = unit.toNanos(timeout);
|
jaroslav@1890
|
376 |
int c = -1;
|
jaroslav@1890
|
377 |
final ReentrantLock putLock = this.putLock;
|
jaroslav@1890
|
378 |
final AtomicInteger count = this.count;
|
jaroslav@1890
|
379 |
putLock.lockInterruptibly();
|
jaroslav@1890
|
380 |
try {
|
jaroslav@1890
|
381 |
while (count.get() == capacity) {
|
jaroslav@1890
|
382 |
if (nanos <= 0)
|
jaroslav@1890
|
383 |
return false;
|
jaroslav@1890
|
384 |
nanos = notFull.awaitNanos(nanos);
|
jaroslav@1890
|
385 |
}
|
jaroslav@1890
|
386 |
enqueue(new Node<E>(e));
|
jaroslav@1890
|
387 |
c = count.getAndIncrement();
|
jaroslav@1890
|
388 |
if (c + 1 < capacity)
|
jaroslav@1890
|
389 |
notFull.signal();
|
jaroslav@1890
|
390 |
} finally {
|
jaroslav@1890
|
391 |
putLock.unlock();
|
jaroslav@1890
|
392 |
}
|
jaroslav@1890
|
393 |
if (c == 0)
|
jaroslav@1890
|
394 |
signalNotEmpty();
|
jaroslav@1890
|
395 |
return true;
|
jaroslav@1890
|
396 |
}
|
jaroslav@1890
|
397 |
|
jaroslav@1890
|
398 |
/**
|
jaroslav@1890
|
399 |
* Inserts the specified element at the tail of this queue if it is
|
jaroslav@1890
|
400 |
* possible to do so immediately without exceeding the queue's capacity,
|
jaroslav@1890
|
401 |
* returning {@code true} upon success and {@code false} if this queue
|
jaroslav@1890
|
402 |
* is full.
|
jaroslav@1890
|
403 |
* When using a capacity-restricted queue, this method is generally
|
jaroslav@1890
|
404 |
* preferable to method {@link BlockingQueue#add add}, which can fail to
|
jaroslav@1890
|
405 |
* insert an element only by throwing an exception.
|
jaroslav@1890
|
406 |
*
|
jaroslav@1890
|
407 |
* @throws NullPointerException if the specified element is null
|
jaroslav@1890
|
408 |
*/
|
jaroslav@1890
|
409 |
public boolean offer(E e) {
|
jaroslav@1890
|
410 |
if (e == null) throw new NullPointerException();
|
jaroslav@1890
|
411 |
final AtomicInteger count = this.count;
|
jaroslav@1890
|
412 |
if (count.get() == capacity)
|
jaroslav@1890
|
413 |
return false;
|
jaroslav@1890
|
414 |
int c = -1;
|
jaroslav@1890
|
415 |
Node<E> node = new Node(e);
|
jaroslav@1890
|
416 |
final ReentrantLock putLock = this.putLock;
|
jaroslav@1890
|
417 |
putLock.lock();
|
jaroslav@1890
|
418 |
try {
|
jaroslav@1890
|
419 |
if (count.get() < capacity) {
|
jaroslav@1890
|
420 |
enqueue(node);
|
jaroslav@1890
|
421 |
c = count.getAndIncrement();
|
jaroslav@1890
|
422 |
if (c + 1 < capacity)
|
jaroslav@1890
|
423 |
notFull.signal();
|
jaroslav@1890
|
424 |
}
|
jaroslav@1890
|
425 |
} finally {
|
jaroslav@1890
|
426 |
putLock.unlock();
|
jaroslav@1890
|
427 |
}
|
jaroslav@1890
|
428 |
if (c == 0)
|
jaroslav@1890
|
429 |
signalNotEmpty();
|
jaroslav@1890
|
430 |
return c >= 0;
|
jaroslav@1890
|
431 |
}
|
jaroslav@1890
|
432 |
|
jaroslav@1890
|
433 |
|
jaroslav@1890
|
434 |
public E take() throws InterruptedException {
|
jaroslav@1890
|
435 |
E x;
|
jaroslav@1890
|
436 |
int c = -1;
|
jaroslav@1890
|
437 |
final AtomicInteger count = this.count;
|
jaroslav@1890
|
438 |
final ReentrantLock takeLock = this.takeLock;
|
jaroslav@1890
|
439 |
takeLock.lockInterruptibly();
|
jaroslav@1890
|
440 |
try {
|
jaroslav@1890
|
441 |
while (count.get() == 0) {
|
jaroslav@1890
|
442 |
notEmpty.await();
|
jaroslav@1890
|
443 |
}
|
jaroslav@1890
|
444 |
x = dequeue();
|
jaroslav@1890
|
445 |
c = count.getAndDecrement();
|
jaroslav@1890
|
446 |
if (c > 1)
|
jaroslav@1890
|
447 |
notEmpty.signal();
|
jaroslav@1890
|
448 |
} finally {
|
jaroslav@1890
|
449 |
takeLock.unlock();
|
jaroslav@1890
|
450 |
}
|
jaroslav@1890
|
451 |
if (c == capacity)
|
jaroslav@1890
|
452 |
signalNotFull();
|
jaroslav@1890
|
453 |
return x;
|
jaroslav@1890
|
454 |
}
|
jaroslav@1890
|
455 |
|
jaroslav@1890
|
456 |
public E poll(long timeout, TimeUnit unit) throws InterruptedException {
|
jaroslav@1890
|
457 |
E x = null;
|
jaroslav@1890
|
458 |
int c = -1;
|
jaroslav@1890
|
459 |
long nanos = unit.toNanos(timeout);
|
jaroslav@1890
|
460 |
final AtomicInteger count = this.count;
|
jaroslav@1890
|
461 |
final ReentrantLock takeLock = this.takeLock;
|
jaroslav@1890
|
462 |
takeLock.lockInterruptibly();
|
jaroslav@1890
|
463 |
try {
|
jaroslav@1890
|
464 |
while (count.get() == 0) {
|
jaroslav@1890
|
465 |
if (nanos <= 0)
|
jaroslav@1890
|
466 |
return null;
|
jaroslav@1890
|
467 |
nanos = notEmpty.awaitNanos(nanos);
|
jaroslav@1890
|
468 |
}
|
jaroslav@1890
|
469 |
x = dequeue();
|
jaroslav@1890
|
470 |
c = count.getAndDecrement();
|
jaroslav@1890
|
471 |
if (c > 1)
|
jaroslav@1890
|
472 |
notEmpty.signal();
|
jaroslav@1890
|
473 |
} finally {
|
jaroslav@1890
|
474 |
takeLock.unlock();
|
jaroslav@1890
|
475 |
}
|
jaroslav@1890
|
476 |
if (c == capacity)
|
jaroslav@1890
|
477 |
signalNotFull();
|
jaroslav@1890
|
478 |
return x;
|
jaroslav@1890
|
479 |
}
|
jaroslav@1890
|
480 |
|
jaroslav@1890
|
481 |
public E poll() {
|
jaroslav@1890
|
482 |
final AtomicInteger count = this.count;
|
jaroslav@1890
|
483 |
if (count.get() == 0)
|
jaroslav@1890
|
484 |
return null;
|
jaroslav@1890
|
485 |
E x = null;
|
jaroslav@1890
|
486 |
int c = -1;
|
jaroslav@1890
|
487 |
final ReentrantLock takeLock = this.takeLock;
|
jaroslav@1890
|
488 |
takeLock.lock();
|
jaroslav@1890
|
489 |
try {
|
jaroslav@1890
|
490 |
if (count.get() > 0) {
|
jaroslav@1890
|
491 |
x = dequeue();
|
jaroslav@1890
|
492 |
c = count.getAndDecrement();
|
jaroslav@1890
|
493 |
if (c > 1)
|
jaroslav@1890
|
494 |
notEmpty.signal();
|
jaroslav@1890
|
495 |
}
|
jaroslav@1890
|
496 |
} finally {
|
jaroslav@1890
|
497 |
takeLock.unlock();
|
jaroslav@1890
|
498 |
}
|
jaroslav@1890
|
499 |
if (c == capacity)
|
jaroslav@1890
|
500 |
signalNotFull();
|
jaroslav@1890
|
501 |
return x;
|
jaroslav@1890
|
502 |
}
|
jaroslav@1890
|
503 |
|
jaroslav@1890
|
504 |
public E peek() {
|
jaroslav@1890
|
505 |
if (count.get() == 0)
|
jaroslav@1890
|
506 |
return null;
|
jaroslav@1890
|
507 |
final ReentrantLock takeLock = this.takeLock;
|
jaroslav@1890
|
508 |
takeLock.lock();
|
jaroslav@1890
|
509 |
try {
|
jaroslav@1890
|
510 |
Node<E> first = head.next;
|
jaroslav@1890
|
511 |
if (first == null)
|
jaroslav@1890
|
512 |
return null;
|
jaroslav@1890
|
513 |
else
|
jaroslav@1890
|
514 |
return first.item;
|
jaroslav@1890
|
515 |
} finally {
|
jaroslav@1890
|
516 |
takeLock.unlock();
|
jaroslav@1890
|
517 |
}
|
jaroslav@1890
|
518 |
}
|
jaroslav@1890
|
519 |
|
jaroslav@1890
|
520 |
/**
|
jaroslav@1890
|
521 |
* Unlinks interior Node p with predecessor trail.
|
jaroslav@1890
|
522 |
*/
|
jaroslav@1890
|
523 |
void unlink(Node<E> p, Node<E> trail) {
|
jaroslav@1890
|
524 |
// assert isFullyLocked();
|
jaroslav@1890
|
525 |
// p.next is not changed, to allow iterators that are
|
jaroslav@1890
|
526 |
// traversing p to maintain their weak-consistency guarantee.
|
jaroslav@1890
|
527 |
p.item = null;
|
jaroslav@1890
|
528 |
trail.next = p.next;
|
jaroslav@1890
|
529 |
if (last == p)
|
jaroslav@1890
|
530 |
last = trail;
|
jaroslav@1890
|
531 |
if (count.getAndDecrement() == capacity)
|
jaroslav@1890
|
532 |
notFull.signal();
|
jaroslav@1890
|
533 |
}
|
jaroslav@1890
|
534 |
|
jaroslav@1890
|
535 |
/**
|
jaroslav@1890
|
536 |
* Removes a single instance of the specified element from this queue,
|
jaroslav@1890
|
537 |
* if it is present. More formally, removes an element {@code e} such
|
jaroslav@1890
|
538 |
* that {@code o.equals(e)}, if this queue contains one or more such
|
jaroslav@1890
|
539 |
* elements.
|
jaroslav@1890
|
540 |
* Returns {@code true} if this queue contained the specified element
|
jaroslav@1890
|
541 |
* (or equivalently, if this queue changed as a result of the call).
|
jaroslav@1890
|
542 |
*
|
jaroslav@1890
|
543 |
* @param o element to be removed from this queue, if present
|
jaroslav@1890
|
544 |
* @return {@code true} if this queue changed as a result of the call
|
jaroslav@1890
|
545 |
*/
|
jaroslav@1890
|
546 |
public boolean remove(Object o) {
|
jaroslav@1890
|
547 |
if (o == null) return false;
|
jaroslav@1890
|
548 |
fullyLock();
|
jaroslav@1890
|
549 |
try {
|
jaroslav@1890
|
550 |
for (Node<E> trail = head, p = trail.next;
|
jaroslav@1890
|
551 |
p != null;
|
jaroslav@1890
|
552 |
trail = p, p = p.next) {
|
jaroslav@1890
|
553 |
if (o.equals(p.item)) {
|
jaroslav@1890
|
554 |
unlink(p, trail);
|
jaroslav@1890
|
555 |
return true;
|
jaroslav@1890
|
556 |
}
|
jaroslav@1890
|
557 |
}
|
jaroslav@1890
|
558 |
return false;
|
jaroslav@1890
|
559 |
} finally {
|
jaroslav@1890
|
560 |
fullyUnlock();
|
jaroslav@1890
|
561 |
}
|
jaroslav@1890
|
562 |
}
|
jaroslav@1890
|
563 |
|
jaroslav@1890
|
564 |
/**
|
jaroslav@1890
|
565 |
* Returns {@code true} if this queue contains the specified element.
|
jaroslav@1890
|
566 |
* More formally, returns {@code true} if and only if this queue contains
|
jaroslav@1890
|
567 |
* at least one element {@code e} such that {@code o.equals(e)}.
|
jaroslav@1890
|
568 |
*
|
jaroslav@1890
|
569 |
* @param o object to be checked for containment in this queue
|
jaroslav@1890
|
570 |
* @return {@code true} if this queue contains the specified element
|
jaroslav@1890
|
571 |
*/
|
jaroslav@1890
|
572 |
public boolean contains(Object o) {
|
jaroslav@1890
|
573 |
if (o == null) return false;
|
jaroslav@1890
|
574 |
fullyLock();
|
jaroslav@1890
|
575 |
try {
|
jaroslav@1890
|
576 |
for (Node<E> p = head.next; p != null; p = p.next)
|
jaroslav@1890
|
577 |
if (o.equals(p.item))
|
jaroslav@1890
|
578 |
return true;
|
jaroslav@1890
|
579 |
return false;
|
jaroslav@1890
|
580 |
} finally {
|
jaroslav@1890
|
581 |
fullyUnlock();
|
jaroslav@1890
|
582 |
}
|
jaroslav@1890
|
583 |
}
|
jaroslav@1890
|
584 |
|
jaroslav@1890
|
585 |
/**
|
jaroslav@1890
|
586 |
* Returns an array containing all of the elements in this queue, in
|
jaroslav@1890
|
587 |
* proper sequence.
|
jaroslav@1890
|
588 |
*
|
jaroslav@1890
|
589 |
* <p>The returned array will be "safe" in that no references to it are
|
jaroslav@1890
|
590 |
* maintained by this queue. (In other words, this method must allocate
|
jaroslav@1890
|
591 |
* a new array). The caller is thus free to modify the returned array.
|
jaroslav@1890
|
592 |
*
|
jaroslav@1890
|
593 |
* <p>This method acts as bridge between array-based and collection-based
|
jaroslav@1890
|
594 |
* APIs.
|
jaroslav@1890
|
595 |
*
|
jaroslav@1890
|
596 |
* @return an array containing all of the elements in this queue
|
jaroslav@1890
|
597 |
*/
|
jaroslav@1890
|
598 |
public Object[] toArray() {
|
jaroslav@1890
|
599 |
fullyLock();
|
jaroslav@1890
|
600 |
try {
|
jaroslav@1890
|
601 |
int size = count.get();
|
jaroslav@1890
|
602 |
Object[] a = new Object[size];
|
jaroslav@1890
|
603 |
int k = 0;
|
jaroslav@1890
|
604 |
for (Node<E> p = head.next; p != null; p = p.next)
|
jaroslav@1890
|
605 |
a[k++] = p.item;
|
jaroslav@1890
|
606 |
return a;
|
jaroslav@1890
|
607 |
} finally {
|
jaroslav@1890
|
608 |
fullyUnlock();
|
jaroslav@1890
|
609 |
}
|
jaroslav@1890
|
610 |
}
|
jaroslav@1890
|
611 |
|
jaroslav@1890
|
612 |
/**
|
jaroslav@1890
|
613 |
* Returns an array containing all of the elements in this queue, in
|
jaroslav@1890
|
614 |
* proper sequence; the runtime type of the returned array is that of
|
jaroslav@1890
|
615 |
* the specified array. If the queue fits in the specified array, it
|
jaroslav@1890
|
616 |
* is returned therein. Otherwise, a new array is allocated with the
|
jaroslav@1890
|
617 |
* runtime type of the specified array and the size of this queue.
|
jaroslav@1890
|
618 |
*
|
jaroslav@1890
|
619 |
* <p>If this queue fits in the specified array with room to spare
|
jaroslav@1890
|
620 |
* (i.e., the array has more elements than this queue), the element in
|
jaroslav@1890
|
621 |
* the array immediately following the end of the queue is set to
|
jaroslav@1890
|
622 |
* {@code null}.
|
jaroslav@1890
|
623 |
*
|
jaroslav@1890
|
624 |
* <p>Like the {@link #toArray()} method, this method acts as bridge between
|
jaroslav@1890
|
625 |
* array-based and collection-based APIs. Further, this method allows
|
jaroslav@1890
|
626 |
* precise control over the runtime type of the output array, and may,
|
jaroslav@1890
|
627 |
* under certain circumstances, be used to save allocation costs.
|
jaroslav@1890
|
628 |
*
|
jaroslav@1890
|
629 |
* <p>Suppose {@code x} is a queue known to contain only strings.
|
jaroslav@1890
|
630 |
* The following code can be used to dump the queue into a newly
|
jaroslav@1890
|
631 |
* allocated array of {@code String}:
|
jaroslav@1890
|
632 |
*
|
jaroslav@1890
|
633 |
* <pre>
|
jaroslav@1890
|
634 |
* String[] y = x.toArray(new String[0]);</pre>
|
jaroslav@1890
|
635 |
*
|
jaroslav@1890
|
636 |
* Note that {@code toArray(new Object[0])} is identical in function to
|
jaroslav@1890
|
637 |
* {@code toArray()}.
|
jaroslav@1890
|
638 |
*
|
jaroslav@1890
|
639 |
* @param a the array into which the elements of the queue are to
|
jaroslav@1890
|
640 |
* be stored, if it is big enough; otherwise, a new array of the
|
jaroslav@1890
|
641 |
* same runtime type is allocated for this purpose
|
jaroslav@1890
|
642 |
* @return an array containing all of the elements in this queue
|
jaroslav@1890
|
643 |
* @throws ArrayStoreException if the runtime type of the specified array
|
jaroslav@1890
|
644 |
* is not a supertype of the runtime type of every element in
|
jaroslav@1890
|
645 |
* this queue
|
jaroslav@1890
|
646 |
* @throws NullPointerException if the specified array is null
|
jaroslav@1890
|
647 |
*/
|
jaroslav@1890
|
648 |
@SuppressWarnings("unchecked")
|
jaroslav@1890
|
649 |
public <T> T[] toArray(T[] a) {
|
jaroslav@1890
|
650 |
fullyLock();
|
jaroslav@1890
|
651 |
try {
|
jaroslav@1890
|
652 |
int size = count.get();
|
jaroslav@1890
|
653 |
if (a.length < size)
|
jaroslav@1890
|
654 |
a = (T[])java.lang.reflect.Array.newInstance
|
jaroslav@1890
|
655 |
(a.getClass().getComponentType(), size);
|
jaroslav@1890
|
656 |
|
jaroslav@1890
|
657 |
int k = 0;
|
jaroslav@1890
|
658 |
for (Node<E> p = head.next; p != null; p = p.next)
|
jaroslav@1890
|
659 |
a[k++] = (T)p.item;
|
jaroslav@1890
|
660 |
if (a.length > k)
|
jaroslav@1890
|
661 |
a[k] = null;
|
jaroslav@1890
|
662 |
return a;
|
jaroslav@1890
|
663 |
} finally {
|
jaroslav@1890
|
664 |
fullyUnlock();
|
jaroslav@1890
|
665 |
}
|
jaroslav@1890
|
666 |
}
|
jaroslav@1890
|
667 |
|
jaroslav@1890
|
668 |
public String toString() {
|
jaroslav@1890
|
669 |
fullyLock();
|
jaroslav@1890
|
670 |
try {
|
jaroslav@1890
|
671 |
Node<E> p = head.next;
|
jaroslav@1890
|
672 |
if (p == null)
|
jaroslav@1890
|
673 |
return "[]";
|
jaroslav@1890
|
674 |
|
jaroslav@1890
|
675 |
StringBuilder sb = new StringBuilder();
|
jaroslav@1890
|
676 |
sb.append('[');
|
jaroslav@1890
|
677 |
for (;;) {
|
jaroslav@1890
|
678 |
E e = p.item;
|
jaroslav@1890
|
679 |
sb.append(e == this ? "(this Collection)" : e);
|
jaroslav@1890
|
680 |
p = p.next;
|
jaroslav@1890
|
681 |
if (p == null)
|
jaroslav@1890
|
682 |
return sb.append(']').toString();
|
jaroslav@1890
|
683 |
sb.append(',').append(' ');
|
jaroslav@1890
|
684 |
}
|
jaroslav@1890
|
685 |
} finally {
|
jaroslav@1890
|
686 |
fullyUnlock();
|
jaroslav@1890
|
687 |
}
|
jaroslav@1890
|
688 |
}
|
jaroslav@1890
|
689 |
|
jaroslav@1890
|
690 |
/**
|
jaroslav@1890
|
691 |
* Atomically removes all of the elements from this queue.
|
jaroslav@1890
|
692 |
* The queue will be empty after this call returns.
|
jaroslav@1890
|
693 |
*/
|
jaroslav@1890
|
694 |
public void clear() {
|
jaroslav@1890
|
695 |
fullyLock();
|
jaroslav@1890
|
696 |
try {
|
jaroslav@1890
|
697 |
for (Node<E> p, h = head; (p = h.next) != null; h = p) {
|
jaroslav@1890
|
698 |
h.next = h;
|
jaroslav@1890
|
699 |
p.item = null;
|
jaroslav@1890
|
700 |
}
|
jaroslav@1890
|
701 |
head = last;
|
jaroslav@1890
|
702 |
// assert head.item == null && head.next == null;
|
jaroslav@1890
|
703 |
if (count.getAndSet(0) == capacity)
|
jaroslav@1890
|
704 |
notFull.signal();
|
jaroslav@1890
|
705 |
} finally {
|
jaroslav@1890
|
706 |
fullyUnlock();
|
jaroslav@1890
|
707 |
}
|
jaroslav@1890
|
708 |
}
|
jaroslav@1890
|
709 |
|
jaroslav@1890
|
710 |
/**
|
jaroslav@1890
|
711 |
* @throws UnsupportedOperationException {@inheritDoc}
|
jaroslav@1890
|
712 |
* @throws ClassCastException {@inheritDoc}
|
jaroslav@1890
|
713 |
* @throws NullPointerException {@inheritDoc}
|
jaroslav@1890
|
714 |
* @throws IllegalArgumentException {@inheritDoc}
|
jaroslav@1890
|
715 |
*/
|
jaroslav@1890
|
716 |
public int drainTo(Collection<? super E> c) {
|
jaroslav@1890
|
717 |
return drainTo(c, Integer.MAX_VALUE);
|
jaroslav@1890
|
718 |
}
|
jaroslav@1890
|
719 |
|
jaroslav@1890
|
720 |
/**
|
jaroslav@1890
|
721 |
* @throws UnsupportedOperationException {@inheritDoc}
|
jaroslav@1890
|
722 |
* @throws ClassCastException {@inheritDoc}
|
jaroslav@1890
|
723 |
* @throws NullPointerException {@inheritDoc}
|
jaroslav@1890
|
724 |
* @throws IllegalArgumentException {@inheritDoc}
|
jaroslav@1890
|
725 |
*/
|
jaroslav@1890
|
726 |
public int drainTo(Collection<? super E> c, int maxElements) {
|
jaroslav@1890
|
727 |
if (c == null)
|
jaroslav@1890
|
728 |
throw new NullPointerException();
|
jaroslav@1890
|
729 |
if (c == this)
|
jaroslav@1890
|
730 |
throw new IllegalArgumentException();
|
jaroslav@1890
|
731 |
boolean signalNotFull = false;
|
jaroslav@1890
|
732 |
final ReentrantLock takeLock = this.takeLock;
|
jaroslav@1890
|
733 |
takeLock.lock();
|
jaroslav@1890
|
734 |
try {
|
jaroslav@1890
|
735 |
int n = Math.min(maxElements, count.get());
|
jaroslav@1890
|
736 |
// count.get provides visibility to first n Nodes
|
jaroslav@1890
|
737 |
Node<E> h = head;
|
jaroslav@1890
|
738 |
int i = 0;
|
jaroslav@1890
|
739 |
try {
|
jaroslav@1890
|
740 |
while (i < n) {
|
jaroslav@1890
|
741 |
Node<E> p = h.next;
|
jaroslav@1890
|
742 |
c.add(p.item);
|
jaroslav@1890
|
743 |
p.item = null;
|
jaroslav@1890
|
744 |
h.next = h;
|
jaroslav@1890
|
745 |
h = p;
|
jaroslav@1890
|
746 |
++i;
|
jaroslav@1890
|
747 |
}
|
jaroslav@1890
|
748 |
return n;
|
jaroslav@1890
|
749 |
} finally {
|
jaroslav@1890
|
750 |
// Restore invariants even if c.add() threw
|
jaroslav@1890
|
751 |
if (i > 0) {
|
jaroslav@1890
|
752 |
// assert h.item == null;
|
jaroslav@1890
|
753 |
head = h;
|
jaroslav@1890
|
754 |
signalNotFull = (count.getAndAdd(-i) == capacity);
|
jaroslav@1890
|
755 |
}
|
jaroslav@1890
|
756 |
}
|
jaroslav@1890
|
757 |
} finally {
|
jaroslav@1890
|
758 |
takeLock.unlock();
|
jaroslav@1890
|
759 |
if (signalNotFull)
|
jaroslav@1890
|
760 |
signalNotFull();
|
jaroslav@1890
|
761 |
}
|
jaroslav@1890
|
762 |
}
|
jaroslav@1890
|
763 |
|
jaroslav@1890
|
764 |
/**
|
jaroslav@1890
|
765 |
* Returns an iterator over the elements in this queue in proper sequence.
|
jaroslav@1890
|
766 |
* The elements will be returned in order from first (head) to last (tail).
|
jaroslav@1890
|
767 |
*
|
jaroslav@1890
|
768 |
* <p>The returned iterator is a "weakly consistent" iterator that
|
jaroslav@1890
|
769 |
* will never throw {@link java.util.ConcurrentModificationException
|
jaroslav@1890
|
770 |
* ConcurrentModificationException}, and guarantees to traverse
|
jaroslav@1890
|
771 |
* elements as they existed upon construction of the iterator, and
|
jaroslav@1890
|
772 |
* may (but is not guaranteed to) reflect any modifications
|
jaroslav@1890
|
773 |
* subsequent to construction.
|
jaroslav@1890
|
774 |
*
|
jaroslav@1890
|
775 |
* @return an iterator over the elements in this queue in proper sequence
|
jaroslav@1890
|
776 |
*/
|
jaroslav@1890
|
777 |
public Iterator<E> iterator() {
|
jaroslav@1890
|
778 |
return new Itr();
|
jaroslav@1890
|
779 |
}
|
jaroslav@1890
|
780 |
|
jaroslav@1890
|
781 |
private class Itr implements Iterator<E> {
|
jaroslav@1890
|
782 |
/*
|
jaroslav@1890
|
783 |
* Basic weakly-consistent iterator. At all times hold the next
|
jaroslav@1890
|
784 |
* item to hand out so that if hasNext() reports true, we will
|
jaroslav@1890
|
785 |
* still have it to return even if lost race with a take etc.
|
jaroslav@1890
|
786 |
*/
|
jaroslav@1890
|
787 |
private Node<E> current;
|
jaroslav@1890
|
788 |
private Node<E> lastRet;
|
jaroslav@1890
|
789 |
private E currentElement;
|
jaroslav@1890
|
790 |
|
jaroslav@1890
|
791 |
Itr() {
|
jaroslav@1890
|
792 |
fullyLock();
|
jaroslav@1890
|
793 |
try {
|
jaroslav@1890
|
794 |
current = head.next;
|
jaroslav@1890
|
795 |
if (current != null)
|
jaroslav@1890
|
796 |
currentElement = current.item;
|
jaroslav@1890
|
797 |
} finally {
|
jaroslav@1890
|
798 |
fullyUnlock();
|
jaroslav@1890
|
799 |
}
|
jaroslav@1890
|
800 |
}
|
jaroslav@1890
|
801 |
|
jaroslav@1890
|
802 |
public boolean hasNext() {
|
jaroslav@1890
|
803 |
return current != null;
|
jaroslav@1890
|
804 |
}
|
jaroslav@1890
|
805 |
|
jaroslav@1890
|
806 |
/**
|
jaroslav@1890
|
807 |
* Returns the next live successor of p, or null if no such.
|
jaroslav@1890
|
808 |
*
|
jaroslav@1890
|
809 |
* Unlike other traversal methods, iterators need to handle both:
|
jaroslav@1890
|
810 |
* - dequeued nodes (p.next == p)
|
jaroslav@1890
|
811 |
* - (possibly multiple) interior removed nodes (p.item == null)
|
jaroslav@1890
|
812 |
*/
|
jaroslav@1890
|
813 |
private Node<E> nextNode(Node<E> p) {
|
jaroslav@1890
|
814 |
for (;;) {
|
jaroslav@1890
|
815 |
Node<E> s = p.next;
|
jaroslav@1890
|
816 |
if (s == p)
|
jaroslav@1890
|
817 |
return head.next;
|
jaroslav@1890
|
818 |
if (s == null || s.item != null)
|
jaroslav@1890
|
819 |
return s;
|
jaroslav@1890
|
820 |
p = s;
|
jaroslav@1890
|
821 |
}
|
jaroslav@1890
|
822 |
}
|
jaroslav@1890
|
823 |
|
jaroslav@1890
|
824 |
public E next() {
|
jaroslav@1890
|
825 |
fullyLock();
|
jaroslav@1890
|
826 |
try {
|
jaroslav@1890
|
827 |
if (current == null)
|
jaroslav@1890
|
828 |
throw new NoSuchElementException();
|
jaroslav@1890
|
829 |
E x = currentElement;
|
jaroslav@1890
|
830 |
lastRet = current;
|
jaroslav@1890
|
831 |
current = nextNode(current);
|
jaroslav@1890
|
832 |
currentElement = (current == null) ? null : current.item;
|
jaroslav@1890
|
833 |
return x;
|
jaroslav@1890
|
834 |
} finally {
|
jaroslav@1890
|
835 |
fullyUnlock();
|
jaroslav@1890
|
836 |
}
|
jaroslav@1890
|
837 |
}
|
jaroslav@1890
|
838 |
|
jaroslav@1890
|
839 |
public void remove() {
|
jaroslav@1890
|
840 |
if (lastRet == null)
|
jaroslav@1890
|
841 |
throw new IllegalStateException();
|
jaroslav@1890
|
842 |
fullyLock();
|
jaroslav@1890
|
843 |
try {
|
jaroslav@1890
|
844 |
Node<E> node = lastRet;
|
jaroslav@1890
|
845 |
lastRet = null;
|
jaroslav@1890
|
846 |
for (Node<E> trail = head, p = trail.next;
|
jaroslav@1890
|
847 |
p != null;
|
jaroslav@1890
|
848 |
trail = p, p = p.next) {
|
jaroslav@1890
|
849 |
if (p == node) {
|
jaroslav@1890
|
850 |
unlink(p, trail);
|
jaroslav@1890
|
851 |
break;
|
jaroslav@1890
|
852 |
}
|
jaroslav@1890
|
853 |
}
|
jaroslav@1890
|
854 |
} finally {
|
jaroslav@1890
|
855 |
fullyUnlock();
|
jaroslav@1890
|
856 |
}
|
jaroslav@1890
|
857 |
}
|
jaroslav@1890
|
858 |
}
|
jaroslav@1890
|
859 |
|
jaroslav@1890
|
860 |
/**
|
jaroslav@1890
|
861 |
* Save the state to a stream (that is, serialize it).
|
jaroslav@1890
|
862 |
*
|
jaroslav@1890
|
863 |
* @serialData The capacity is emitted (int), followed by all of
|
jaroslav@1890
|
864 |
* its elements (each an {@code Object}) in the proper order,
|
jaroslav@1890
|
865 |
* followed by a null
|
jaroslav@1890
|
866 |
* @param s the stream
|
jaroslav@1890
|
867 |
*/
|
jaroslav@1890
|
868 |
private void writeObject(java.io.ObjectOutputStream s)
|
jaroslav@1890
|
869 |
throws java.io.IOException {
|
jaroslav@1890
|
870 |
|
jaroslav@1890
|
871 |
fullyLock();
|
jaroslav@1890
|
872 |
try {
|
jaroslav@1890
|
873 |
// Write out any hidden stuff, plus capacity
|
jaroslav@1890
|
874 |
s.defaultWriteObject();
|
jaroslav@1890
|
875 |
|
jaroslav@1890
|
876 |
// Write out all elements in the proper order.
|
jaroslav@1890
|
877 |
for (Node<E> p = head.next; p != null; p = p.next)
|
jaroslav@1890
|
878 |
s.writeObject(p.item);
|
jaroslav@1890
|
879 |
|
jaroslav@1890
|
880 |
// Use trailing null as sentinel
|
jaroslav@1890
|
881 |
s.writeObject(null);
|
jaroslav@1890
|
882 |
} finally {
|
jaroslav@1890
|
883 |
fullyUnlock();
|
jaroslav@1890
|
884 |
}
|
jaroslav@1890
|
885 |
}
|
jaroslav@1890
|
886 |
|
jaroslav@1890
|
887 |
/**
|
jaroslav@1890
|
888 |
* Reconstitute this queue instance from a stream (that is,
|
jaroslav@1890
|
889 |
* deserialize it).
|
jaroslav@1890
|
890 |
*
|
jaroslav@1890
|
891 |
* @param s the stream
|
jaroslav@1890
|
892 |
*/
|
jaroslav@1890
|
893 |
private void readObject(java.io.ObjectInputStream s)
|
jaroslav@1890
|
894 |
throws java.io.IOException, ClassNotFoundException {
|
jaroslav@1890
|
895 |
// Read in capacity, and any hidden stuff
|
jaroslav@1890
|
896 |
s.defaultReadObject();
|
jaroslav@1890
|
897 |
|
jaroslav@1890
|
898 |
count.set(0);
|
jaroslav@1890
|
899 |
last = head = new Node<E>(null);
|
jaroslav@1890
|
900 |
|
jaroslav@1890
|
901 |
// Read in all elements and place in queue
|
jaroslav@1890
|
902 |
for (;;) {
|
jaroslav@1890
|
903 |
@SuppressWarnings("unchecked")
|
jaroslav@1890
|
904 |
E item = (E)s.readObject();
|
jaroslav@1890
|
905 |
if (item == null)
|
jaroslav@1890
|
906 |
break;
|
jaroslav@1890
|
907 |
add(item);
|
jaroslav@1890
|
908 |
}
|
jaroslav@1890
|
909 |
}
|
jaroslav@1890
|
910 |
}
|