阻塞队列之LinkedBlockingQueue 源码

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package java.util.concurrent;

import java.util.concurrent.atomic.*;

import java.util.concurrent.locks.*;

import java.util.*;

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?* @since 1.5

?* @author Doug Lea

?* @param <E> the type of elements held in this collection

?*

?*/

public class LinkedBlockingQueue<E> extends AbstractQueue<E>

? ? ? ? implements BlockingQueue<E>, java.io.Serializable {

? ? private static final long serialVersionUID = -6903933977591709194L;

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? ? /**

? ? ?* Linked list node class

? ? ?*/

? ? static class Node<E> {

? ? ? ? E item;

? ? ? ? /**

? ? ? ? ?* One of:

? ? ? ? ?* - the real successor Node

? ? ? ? ?* - this Node, meaning the successor is head.next

? ? ? ? ?* - null, meaning there is no successor (this is the last node)

? ? ? ? ?*/

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? ? ? ? Node<E> next;

? ? ? ? Node(E x) { item = x; }

? ? }

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? ? /** The capacity bound, or Integer.MAX_VALUE if none */

? ? private final int capacity;

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? ? /** Current number of elements */

? ? private final AtomicInteger count = new AtomicInteger(0);

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? ? /** Head of linked list */

? ? private transient Node<E> head;

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? ? /** Tail of linked list */

? ? private transient Node<E> last;

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? ? /** Lock held by take, poll, etc */

? ? private final ReentrantLock takeLock = new ReentrantLock();

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? ? /** Wait queue for waiting takes */

? ? private final Condition notEmpty = takeLock.newCondition();

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? ? /** Lock held by put, offer, etc */

? ? private final ReentrantLock putLock = new ReentrantLock();

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? ? /** Wait queue for waiting puts */

? ? private final Condition notFull = putLock.newCondition();

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? ? /**

? ? ?* Signals a waiting take. Called only from put/offer (which do not

? ? ?* otherwise ordinarily lock takeLock.)

? ? ?*/

? ? private void signalNotEmpty() {

? ? ? ? final ReentrantLock takeLock = this.takeLock;

? ? ? ? takeLock.lock();

? ? ? ? try {

? ? ? ? ? ? notEmpty.signal();

? ? ? ? } finally {

? ? ? ? ? ? takeLock.unlock();

? ? ? ? }

? ? }

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? ? /**

? ? ?* Signals a waiting put. Called only from take/poll.

? ? ?*/

? ? private void signalNotFull() {

? ? ? ? final ReentrantLock putLock = this.putLock;

? ? ? ? putLock.lock();

? ? ? ? try {

? ? ? ? ? ? notFull.signal();

? ? ? ? } finally {

? ? ? ? ? ? putLock.unlock();

? ? ? ? }

? ? }

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? ? /**

? ? ?*?创建一个节点，并将其链接在队列的末端.

? ? ?* @param x the item

? ? ?*/

? ? private void enqueue(E x) {

? ? ? ? // assert putLock.isHeldByCurrentThread();

? ? ? ? last = last.next = new Node<E>(x);

? ? }

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? ? /**

? ? ?*?从队列的顶端删除一个节点。

? ? ?