Java:使用Executors创建和管理线程
Java:使用Executors创建和管理线程1.?类?Executors此类中提供的一些方法有：1.1 public static ExecutorService newCachedThreadPool()创建一个可根据需要创建新线程的线程池，但是在以前构造的线程可用时将重用它们。对于执行很多短期异步任务的程序而言，这些线程池通常可提高程序性能。?1.2 public static ExecutorService newFixedThreadPool(int?nThreads)创建一个可重用固定线程数的线程池，以共享的无界队列方式来运行这些线程。?1.3 public static ExecutorService newSingleThreadExecutor()创建一个使用单个?worker?线程的?Executor，以无界队列方式来运行该线程。?这三个方法都可以配合接口ThreadFactory的实例一起使用。并且返回一个ExecutorService接口的实例。2.?接口?ThreadFactory根据需要创建新线程的对象。使用线程工厂就无需再手工编写对?new Thread?的调用了，从而允许应用程序使用特殊的线程子类、属性等等。此接口最简单的实现就是：class SimpleThreadFactory implements ThreadFactory {???public Thread newThread(Runnable r) {?????return new Thread(r);???}?}3.?接口ExecutorService该接口提供了管理终止的方法。4.创建标准线程池启动线程4.1?提供一个简单的实现Runnable接口的线程MyThread.javapackage?com.zj.concurrency.executors;?public?class?MyThread?implements?Runnable {????private?int?count?= 1,?number;?????public?MyThread(int?num) {???????number?= num;???????System.out.println("Create Thread-"?+?number);????}?????public?void?run() {???????while?(true) {???????????System.out.println("Thread-"?+?number?+?" run "?+?count+" time(s)");???????????if?(++count?== 3)??????????????return;???????}????}}这个线程会打印出相应的创建和执行信息。?4.2使用CachedThreadPool启动线程CachedThreadPool.javapackage?com.zj.concurrency.executors;import?java.util.concurrent.ExecutorService;import?java.util.concurrent.Executors;?public?class?CachedThreadPool {????public?static?void?main(String[] args) {???????ExecutorService exec = Executors.newCachedThreadPool();???????for?(int?i = 0; i < 5; i++)???????????exec.execute(new?MyThread(i));???????exec.shutdown();????}}结果：Create Thread-0Create Thread-1Create Thread-2Create Thread-3Thread-0 run 1 time(s)Thread-0 run 2 time(s)Thread-1 run 1 time(s)Thread-1 run 2 time(s)Thread-2 run 1 time(s)Thread-2 run 2 time(s)Create Thread-4Thread-4 run 1 time(s)Thread-4 run 2 time(s)Thread-3 run 1 time(s)Thread-3 run 2 time(s)?4.3?使用FixedThreadPool启动线程FixedThreadPool.javapackage?com.zj.concurrency.executors;import?java.util.concurrent.ExecutorService;import?java.util.concurrent.Executors;?public?class?FixedThreadPool {????public?static?void?main(String[] args) {???????ExecutorService exec = Executors.newFixedThreadPool(2);???????for?(int?i = 0; i < 5; i++)???????????exec.execute(new?MyThread(i));???????exec.shutdown();????}}结果：Create Thread-0Create Thread-1Create Thread-2Create Thread-3Create Thread-4Thread-0 run 1 time(s)Thread-0 run 2 time(s)Thread-2 run 1 time(s)Thread-2 run 2 time(s)Thread-3 run 1 time(s)Thread-3 run 2 time(s)Thread-4 run 1 time(s)Thread-4 run 2 time(s)Thread-1 run 1 time(s)Thread-1 run 2 time(s)?4.4?使用SingleThreadExecutor启动线程SingleThreadExecutor.javapackage?com.zj.concurrency.executors;import?java.util.concurrent.ExecutorService;import?java.util.concurrent.Executors;?public?class?SingleThreadExecutor {????public?static?void?main(String[] args) {???????ExecutorService exec = Executors.newSingleThreadExecutor();???????for?(int?i = 0; i < 5; i++)???????????exec.execute(new?MyThread(i));???????exec.shutdown();????}}结果：Create Thread-0Create Thread-1Create Thread-2Create Thread-3Create Thread-4Thread-0 run 1 time(s)Thread-0 run 2 time(s)Thread-1 run 1 time(s)Thread-1 run 2 time(s)Thread-2 run 1 time(s)Thread-2 run 2 time(s)Thread-3 run 1 time(s)Thread-3 run 2 time(s)Thread-4 run 1 time(s)Thread-4 run 2 time(s)5.配合ThreadFactory接口的使用我们试图给线程加入daemon和priority的属性设置。5.1设置后台线程属性DaemonThreadFactory.javapackage?com.zj.concurrency.executors.factory;import?java.util.concurrent.ThreadFactory;?public?class?DaemonThreadFactory?implements?ThreadFactory {????public?Thread newThread(Runnable r) {???????Thread t =?new?Thread(r);???????t.setDaemon(true);???????return?t;????}}?5.2?设置优先级属性最高优先级MaxPriorityThreadFactory.javapackage?com.zj.concurrency.executors.factory;import?java.util.concurrent.ThreadFactory;?public?class?MaxPriorityThreadFactory?implements?ThreadFactory {????public?Thread newThread(Runnable r) {???????Thread t =?new?Thread(r);???????t.setPriority(Thread.MAX_PRIORITY);???????return?t;????}}最低优先级MinPriorityThreadFactory.javapackage?com.zj.concurrency.executors.factory;import?java.util.concurrent.ThreadFactory;?public?class?MinPriorityThreadFactory?implements?ThreadFactory {????public?Thread newThread(Runnable r) {???????Thread t =?new?Thread(r);???????t.setPriority(Thread.MIN_PRIORITY);???????return?t;????}}?5.3启动带有属性设置的线程ExecFromFactory.javapackage?com.zj.concurrency.executors;import?java.util.concurrent.ExecutorService;import?java.util.concurrent.Executors;import?com.zj.concurrency.executors.factory.DaemonThreadFactory;import?com.zj.concurrency.executors.factory.MaxPriorityThreadFactory;import?com.zj.concurrency.executors.factory.MinPriorityThreadFactory;?public?class?ExecFromFactory {????public?static?void?main(String[] args)?throws?Exception {???????ExecutorService defaultExec = Executors.newCachedThreadPool();???????ExecutorService daemonExec = Executors??????????????.newCachedThreadPool(new?DaemonThreadFactory());???????ExecutorService maxPriorityExec = Executors??????????????.newCachedThreadPool(new?MaxPriorityThreadFactory());???????ExecutorService minPriorityExec = Executors??????????????.newCachedThreadPool(new?MinPriorityThreadFactory());???????for?(int?i = 0; i < 10; i++)???????????daemonExec.execute(new?MyThread(i));???????for?(int?i = 10; i < 20; i++)???????????if?(i == 10)??????????????maxPriorityExec.execute(new?MyThread(i));???????????else?if?(i == 11)??????????????minPriorityExec.execute(new?MyThread(i));???????????else??????????????defaultExec.execute(new?MyThread(i));????}}结果：Create Thread-0Create Thread-1Create Thread-2Create Thread-3Thread-0 run 1 time(s)Thread-0 run 2 time(s)Thread-1 run 1 time(s)Thread-1 run 2 time(s)Thread-2 run 1 time(s)Thread-2 run 2 time(s)Create Thread-4Thread-4 run 1 time(s)Thread-4 run 2 time(s)Create Thread-5Thread-5 run 1 time(s)Thread-5 run 2 time(s)Create Thread-6Create Thread-7Thread-7 run 1 time(s)Thread-7 run 2 time(s)Create Thread-8Thread-8 run 1 time(s)Thread-8 run 2 time(s)Create Thread-9Create Thread-10Thread-10 run 1 time(s)Thread-10 run 2 time(s)Create Thread-11Thread-9 run 1 time(s)Thread-9 run 2 time(s)Thread-6 run 1 time(s)Thread-6 run 2 time(s)Thread-3 run 1 time(s)Thread-3 run 2 time(s)Create Thread-12Create Thread-13Create Thread-14Thread-12 run 1 time(s)Thread-12 run 2 time(s)Thread-13 run 1 time(s)Thread-13 run 2 time(s)Create Thread-15Thread-15 run 1 time(s)Thread-15 run 2 time(s)Create Thread-16Thread-16 run 1 time(s)Thread-16 run 2 time(s)Create Thread-17Create Thread-18Create Thread-19Thread-14 run 1 time(s)Thread-14 run 2 time(s)Thread-17 run 1 time(s)Thread-17 run 2 time(s)Thread-18 run 1 time(s)Thread-18 run 2 time(s)Thread-19 run 1 time(s)Thread-19 run 2 time(s)Thread-11 run 1 time(s)Thread-11 run 2 time(s)
