java集合框架arrayblockingqueue應(yīng)用分析

1、java集合框架arrayblockingqueue應(yīng)用分析arrayblockingqueue是一個(gè)由數(shù)組支持的有界阻塞隊(duì)列。此隊(duì)列按fifo （先進(jìn)先出）原則 對(duì)元素進(jìn)行排序。隊(duì)列的頭部是在隊(duì)列中存在時(shí)間最長(zhǎng)的元素queue1. arraydeque,（數(shù)組雙端隊(duì)列）2. priorityqueue,（優(yōu)先級(jí)隊(duì)列）3. concurrentlinkedqueue,（基于鏈表的并發(fā)隊(duì)列）4. delayqueue,（延期阻塞隊(duì)列）（阻塞隊(duì)列實(shí)現(xiàn)了 blockingqueue接口）5. arrayblockingqueue,（基于數(shù)組的并發(fā)阻塞隊(duì)列）6. linkedblockingqueue

2、,（基于鏈表的 fifo 阻塞隊(duì)列）7. linkedblockingdeque,（基于鏈表的fifo雙端阻塞隊(duì)列）8. priorityblockingqueue,（帶優(yōu)先級(jí)的無界阻塞隊(duì)列） 9.synchronousqueue （并發(fā)同步阻塞隊(duì)列）arrayblockingqueue是一個(gè)由數(shù)組支持的有界阻塞隊(duì)列。此隊(duì)列按fifo （先進(jìn)先出）原則對(duì)元素進(jìn)行排序。隊(duì) 列的頭部是在隊(duì)列中存在時(shí)間最長(zhǎng)的元素。隊(duì)列的尾部是在隊(duì)列中存在時(shí)間最短的元素。 新元素插入到隊(duì)列的尾部，隊(duì)列獲取操作則是從隊(duì)列頭部開始獲得元素。這是一個(gè)典型的“有界緩存區(qū)”，固定大小的數(shù)組在其中保持生產(chǎn)者插入的元素和使用者提

3、取的元素。一旦創(chuàng)建了這樣的緩存區(qū)，就不能再增加其容量。試圖向已滿隊(duì)列中放入元素 會(huì)導(dǎo)致操作受阻塞；試圖從空隊(duì)列中提取元素將導(dǎo)致類似阻塞。此類支持對(duì)等待的生產(chǎn)者線程和消費(fèi)者線程進(jìn)行排序的可選公平策略。默認(rèn)情況下，不保 證是這種排序。然而，通過將公平性（fairness）設(shè)置為true而構(gòu)造的隊(duì)列允許按照fifo 順序訪問線程。公平性通常會(huì)降低吞吐量，但也減少了可變性和避免了 “不平衡性”。復(fù)制代碼代碼如下：public class arrayblockingqueue<e> extends abstractqueue<e> implements blockingqueue

4、<e>, java.io.serializable /*隊(duì)列元素?cái)?shù)組*/private final e items;/*獲取、刪除元素時(shí)的索引（take, poll或remove操作）*/private int takeindex;/*添加元素時(shí)的索引（put, offer或add操作）*/private int putlndex;/*隊(duì)列元素的數(shù)目*/private int count;/* 鎖 */private final reentrantlock lock;/*獲取操作時(shí)的條件/private final condition notempty;/*插入操作時(shí)的條件/pri

5、vate final condition notfull;超出數(shù)組長(zhǎng)度時(shí)，重設(shè)為ofinal int inc(int i) return (+i = items.length)? 0 : i;*插入元素(在獲得鎖的情況下才調(diào)用)7private void insert(e x) itemsputlndex = x; putlndex = inc(putlndex);+count;notempty.signal();/*獲取并移除元素(在獲得鎖的情況下才調(diào)用)*/private e extract() final e items = this.items;e x = itemstakelndex

6、;itemstakelndex = null;takeindex = inc(takelndex);/移到下一個(gè)位置-count;notfullsignal();return x;/*刪除i位置的元素*/void removeat(int i) final e items = this.items;/ if removing front item, just advanceif (i = takeindex) itemstakelndex = null; takeindex = inc(takelndex); else /把i后面的直到putlndex的元素都向前移動(dòng)一個(gè)位置 for (;)

7、int nexti = inc(i);if (nexti != putlndex) itemsi = itemsnexti; i = nexti;else itemsi = null; putlndex = i;break; -count;notfull.signal();*構(gòu)造方法，指定容量，默認(rèn)策略(不是按照fifo的順序訪問)*/public arrayblockingqueue(int capacity) this(capacity, false);*構(gòu)造方法，指定容量及策略*/public arrayblockingqueue(int capacity, boolean fair)

8、訐(capacity <= 0)throw new hlegalargumentexception();this.items = (e) new objectcapacity;lock = new reentrantlock(fair);notempty = lock.newcondition();notfull = lock.newcondition();*通過集合構(gòu)造 / public arrayblockingqueue(int capacity, boolean fair, collection<? extends e> c) this(capacity, fair)

9、;if (capacity < c.size()throw new ihegalargumentexception();for (lterator<? extends e> it = c.iterator(); it.hasnextf);) add(it.next();/*插入元素到隊(duì)尾(super調(diào)用offer方法)* public boolean add(e e) * if (offer(e)* return true;* else* throw new hlegalstateexception(llqueue full11);*將指定的元素插入到此隊(duì)列的尾部(如果立即可

10、行且不會(huì)超過該隊(duì)列的容量),*在成功時(shí)返回true,如果此隊(duì)列已滿，則拋出hlegalstateexceptiono*/public boolean add(e e) return super.add(e);/*將指定的元素插入到此隊(duì)列的尾部(如果立即可行且不會(huì)超過該隊(duì)列的容量),*在成功時(shí)返回true,如果此隊(duì)列已滿，則返回falseo7public boolean offer(e e) if (e = null) throw new nullpointerexception();final reentrantlock lock = this jock;lock.lock();tryif (

11、count = items .length)return false;else insert(e);return true; finally lock.unlock();/*將指定的元素插入此隊(duì)列的尾部，如果該隊(duì)列已滿，則等待可用的空間。*/public void put(e e) throws interruptedexception if (e = null) throw new nullpointerexception();final e items = this.items;final reentrantlock lock = thisck;lockocklnterruptibly()

12、;trytrywhile (count = itemsength)notfull.await(); catch (interruptedexception ie) notfullsignal(); / propagate to non-interrupted threadthrow ie;insert(e); finally!iock.unlock();/*將指定的元素插入此隊(duì)列的尾部，如果該隊(duì)列已滿，則在到達(dá)指定的等待時(shí)間之前等待 可用的空間。*/public boolean offer(e e, long timeout, timeunit unit)throws interruptede

13、xception if (e = null) throw new nullpointerexception();long nanos = unit.tonanos(timeout);final reentrantlock lock = this.lock;lock.locklnterruptiblyo;try for (;) if (count != items.length) insert(e);return true;if (nanos <= 0)/如果時(shí)間到了就返回return false;trynanos = notfull.awaitnanos(nanos); catch (i

14、nterruptedexception ie) notfull.signal(); / propagate to non-interrupted thread throw ie; finally!iock.unlock();獲取并移除此隊(duì)列的頭，如果此隊(duì)列為空，則返回nullpublic e poll() final reentrantlock lock = this.lock;lock.lock();tryif (count = 0)return null;e x = extract();return x; finally!iock.unlock();獲取并移除此隊(duì)列的頭部，在元素變得可用之

15、前一直等待(如果有必要)。public e take() throws interruptedexception final reentrantlock lock = this.lock;lockocklnterruptibly();trytrywhile (count = 0)notempty.await(); catch (interruptedexception ie) notempty.signal(); / propagate to non-interrupted threadthrow ie;e x = extract();return x; finally!iock.unlock

16、();獲取并移除此隊(duì)列的頭部，在指定的等待時(shí)間前等待可用的元素(如果有必要)。public e poll(long timeout, timellnit unit) throws interruptedexception long nanos = unit.tonanos(timeout);final reentrantlock lock = this jock;lock.locklnterruptibly();tryfor (;) if (count != 0) e x = extract();return x;if (nanos <= 0)return null;trynanos =

17、 notempty.awaitnanos(nanos); catch (interruptedexception ie) notempty.signal(); / propagate to non-interrupted threadthrow ie; finally iock.unlock();獲取但不移除此隊(duì)列的頭；如果此隊(duì)列為空，則返回nullpublic e peek() final reentrantlock lock = this.lock;lock.lock();tryreturn (count = 0) ? null: itemstakelndex; finally lock.

18、unlock();*返回此隊(duì)列中元素的數(shù)量。*/public int size() final reentrantlock lock = this.lock;lock.lock();tryreturn count; finally lock.unlock();*返回在無阻塞的理想情況下(不存在內(nèi)存或資源約束)此隊(duì)列能接受的其他元素?cái)?shù)量。*/public int remainingcapacity() final reentrantlock lock = this.lock;lock.lock();tryreturn items length count; finally!iock.unlock();*從