BlockingQueue

import java.util.concurrent.ArrayBlockingQueue; import java.util.concurrent.BlockingQueue; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors;   /**     本例介紹一個特殊的隊列:BlockingQueue,若是BlockQueue是空的,從BlockingQueue取東西的操做將會被阻斷進入等待狀態,直到BlockingQueue進了東西纔會被喚醒.一樣,若是BlockingQueue是滿的,任何試圖往裏存東西的操做也會被阻斷進入等待狀態,直到BlockingQueue裏有空間纔會被喚醒繼續操做.     本例再次實現11.4線程----條件Condition中介紹的籃子程序,不過這個籃子中最多能放的蘋果數不是1,能夠隨意指定.當籃子滿時,生產者進入等待狀態,當籃子空時,消費者等待.  */ /**     使用BlockingQueue的關鍵技術點以下:     1.BlockingQueue定義的經常使用方法以下:         1)add(anObject):把anObject加到BlockingQueue裏,即若是BlockingQueue能夠容納,則返回true,不然招聘異常         2)offer(anObject):表示若是可能的話,將anObject加到BlockingQueue裏,即若是BlockingQueue能夠容納,則返回true,不然返回false.         3)put(anObject):把anObject加到BlockingQueue裏,若是BlockQueue沒有空間,則調用此方法的線程被阻斷直到BlockingQueue裏面有空間再繼續.         4)poll(time):取走BlockingQueue裏排在首位的對象,若不能當即取出,則能夠等time參數規定的時間,取不到時返回null         5)take():取走BlockingQueue裏排在首位的對象,若BlockingQueue爲空,阻斷進入等待狀態直到Blocking有新的對象被加入爲止     2.BlockingQueue有四個具體的實現類,根據不一樣需求,選擇不一樣的實現類         1)ArrayBlockingQueue:規定大小的BlockingQueue,其構造函數必須帶一個int參數來指明其大小.其所含的對象是以FIFO(先入先出)順序排序的.         2)LinkedBlockingQueue:大小不定的BlockingQueue,若其構造函數帶一個規定大小的參數,生成的BlockingQueue有大小限制,若不帶大小參數,所生成的BlockingQueue的大小由Integer.MAX_VALUE來決定.其所含的對象是以FIFO(先入先出)順序排序的         3)PriorityBlockingQueue:相似於LinkedBlockQueue,但其所含對象的排序不是FIFO,而是依據對象的天然排序順序或者是構造函數的Comparator決定的順序.         4)SynchronousQueue:特殊的BlockingQueue,對其的操做必須是放和取交替完成的.     3.LinkedBlockingQueue和ArrayBlockingQueue比較起來,它們背後所用的數據結構不同,致使LinkedBlockingQueue的數據吞吐量要大於ArrayBlockingQueue,但在線程數量很大時其性能的可預見性低於ArrayBlockingQueue.          */ public class BlockingQueueTest {        /**定義裝蘋果的籃子*/        public static class Basket{               //籃子,可以容納3個蘋果               BlockingQueue<String> basket = new ArrayBlockingQueue<String>(3);               //生產蘋果,放入籃子               public void produce() throws InterruptedException{                      //put方法放入一個蘋果,若basket滿了,等到basket有位置                      basket.put("An apple");               }               //消費蘋果,從籃子中取走               public String consume() throws InterruptedException{                      //take方法取出一個蘋果,若basket爲空,等到basket有蘋果爲止                      return basket.take();               }        }        //測試方法        public static void testBasket(){               final Basket basket = new Basket();//創建一個裝蘋果的籃子               //定義蘋果生產者               class Producer implements Runnable{                      public void run(){                             try{                                    while(true){                                           //生產蘋果                                           System.out.println("生產者準備生產蘋果: " + System.currentTimeMillis());                                           basket.produce();                                           System.out.println("生產者生產蘋果完畢: " + System.currentTimeMillis());                                           //休眠300ms                                           Thread.sleep(300);                                    }                             }catch(InterruptedException ex){                             }                      }               }               //定義蘋果消費者               class Consumer implements Runnable{                      public void run(){                             try{                                    while(true){                                           //消費蘋果                                           System.out.println("消費者準備消費蘋果: " + System.currentTimeMillis());                                           basket.consume();                                           System.out.println("消費者消費蘋果完畢: " + System.currentTimeMillis());                                           //休眠1000ms                                           Thread.sleep(1000);                                    }                             }catch(InterruptedException ex){                             }                      }               }               ExecutorService service = Executors.newCachedThreadPool();               Producer producer = new Producer();               Consumer consumer = new Consumer();               service.submit(producer);               service.submit(consumer);               //程序運行5s後,全部任務中止               try{                      Thread.sleep(5000);               }catch(InterruptedException ex){               }               service.shutdownNow();        }        public static void main(String[] args){               BlockingQueueTest.testBasket();        } }