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()[/u]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)[/u]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()[/u]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 [/u]提供一个简单的实现[/u]Runnable[/u]接口的线程[/u][/u]MyThread.java[/u]

[align=left]package com.zj.concurrency.executors;[/align][align=left] [/align][align=left]public class MyThread implements Runnable {[/align][align=left] private int count = 1, number;[/align][align=left] [/align][align=left] public MyThread(int num) {[/align][align=left] number = num;[/align][align=left] System.out.println("Create Thread-" + number);[/align][align=left] }[/align][align=left] [/align][align=left] public void run() {[/align][align=left] while (true) {[/align][align=left] System.out.println("Thread-" + number + " run " + count+" time(s)");[/align][align=left] if (++count == 3)[/align][align=left] return;[/align][align=left] }[/align][align=left] }[/align]}

这个线程会打印出相应的创建和执行信息。 4.2[/u]使用[/u]CachedThreadPool[/u]启动线程[/u][/u]CachedThreadPool.java[/u]

[align=left]package com.zj.concurrency.executors;[/align][align=left]import java.util.concurrent.ExecutorService;[/align][align=left]import java.util.concurrent.Executors;[/align][align=left] [/align][align=left]public class CachedThreadPool {[/align][align=left] public static void main(String[] args) {[/align][align=left] ExecutorService exec = Executors.newCachedThreadPool();[/align][align=left] for (int i = 0; i < 5; i++)[/align][align=left] exec.execute(new MyThread(i));[/align][align=left] exec.shutdown();[/align][align=left] }[/align]}

结果：[align=left]Create Thread-0[/align][align=left]Create Thread-1[/align][align=left]Create Thread-2[/align][align=left]Create Thread-3[/align][align=left]Thread-0 run 1 time(s)[/align][align=left]Thread-0 run 2 time(s)[/align][align=left]Thread-1 run 1 time(s)[/align][align=left]Thread-1 run 2 time(s)[/align][align=left]Thread-2 run 1 time(s)[/align][align=left]Thread-2 run 2 time(s)[/align][align=left]Create Thread-4[/align][align=left]Thread-4 run 1 time(s)[/align][align=left]Thread-4 run 2 time(s)[/align][align=left]Thread-3 run 1 time(s)[/align]Thread-3 run 2 time(s) 4.3 [/u]使用[/u]FixedThreadPool[/u]启动线程[/u][/u]FixedThreadPool.java[/u]

[align=left]package com.zj.concurrency.executors;[/align][align=left]import java.util.concurrent.ExecutorService;[/align][align=left]import java.util.concurrent.Executors;[/align][align=left] [/align][align=left]public class FixedThreadPool {[/align][align=left] public static void main(String[] args) {[/align][align=left] ExecutorService exec = Executors.newFixedThreadPool(2);[/align][align=left] for (int i = 0; i < 5; i++)[/align][align=left] exec.execute(new MyThread(i));[/align][align=left] exec.shutdown();[/align][align=left] }[/align]}

结果：[align=left]Create Thread-0[/align][align=left]Create Thread-1[/align][align=left]Create Thread-2[/align][align=left]Create Thread-3[/align][align=left]Create Thread-4[/align][align=left]Thread-0 run 1 time(s)[/align][align=left]Thread-0 run 2 time(s)[/align][align=left]Thread-2 run 1 time(s)[/align][align=left]Thread-2 run 2 time(s)[/align][align=left]Thread-3 run 1 time(s)[/align][align=left]Thread-3 run 2 time(s)[/align][align=left]Thread-4 run 1 time(s)[/align][align=left]Thread-4 run 2 time(s)[/align][align=left]Thread-1 run 1 time(s)[/align]Thread-1 run 2 time(s) 4.4 [/u]使用[/u]SingleThreadExecutor[/u]启动线程[/u][/u]SingleThreadExecutor.java[/u]

[align=left]package com.zj.concurrency.executors;[/align][align=left]import java.util.concurrent.ExecutorService;[/align][align=left]import java.util.concurrent.Executors;[/align][align=left] [/align][align=left]public class SingleThreadExecutor {[/align][align=left] public static void main(String[] args) {[/align][align=left] ExecutorService exec = Executors.newSingleThreadExecutor();[/align][align=left] for (int i = 0; i < 5; i++)[/align][align=left] exec.execute(new MyThread(i));[/align][align=left] exec.shutdown();[/align][align=left] }[/align]}

结果：[align=left]Create Thread-0[/align][align=left]Create Thread-1[/align][align=left]Create Thread-2[/align][align=left]Create Thread-3[/align][align=left]Create Thread-4[/align][align=left]Thread-0 run 1 time(s)[/align][align=left]Thread-0 run 2 time(s)[/align][align=left]Thread-1 run 1 time(s)[/align][align=left]Thread-1 run 2 time(s)[/align][align=left]Thread-2 run 1 time(s)[/align][align=left]Thread-2 run 2 time(s)[/align][align=left]Thread-3 run 1 time(s)[/align][align=left]Thread-3 run 2 time(s)[/align][align=left]Thread-4 run 1 time(s)[/align]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[/u]设置后台线程属性[/u][/u]DaemonThreadFactory.java[/u]

[align=left]package com.zj.concurrency.executors.factory;[/align][align=left]import java.util.concurrent.ThreadFactory;[/align][align=left] [/align][align=left]public class DaemonThreadFactory implements ThreadFactory {[/align][align=left] public Thread newThread(Runnable r) {[/align][align=left] Thread t = new Thread(r);[/align][align=left] t.setDaemon(true);[/align][align=left] return t;[/align][align=left] }[/align]}

[/u]5.2 [/u]设置优先级属性[/u][/u]最高优先级[/u]MaxPriorityThreadFactory.java[/u]

[align=left]package com.zj.concurrency.executors.factory;[/align][align=left]import java.util.concurrent.ThreadFactory;[/align][align=left] [/align][align=left]public class MaxPriorityThreadFactory implements ThreadFactory {[/align][align=left] public Thread newThread(Runnable r) {[/align][align=left] Thread t = new Thread(r);[/align][align=left] t.setPriority(Thread.MAX_PRIORITY);[/align][align=left] return t;[/align][align=left] }[/align]}

最低优先级[/u]MinPriorityThreadFactory.java[/u]

[align=left]package com.zj.concurrency.executors.factory;[/align][align=left]import java.util.concurrent.ThreadFactory;[/align][align=left] [/align][align=left]public class MinPriorityThreadFactory implements ThreadFactory {[/align][align=left] public Thread newThread(Runnable r) {[/align][align=left] Thread t = new Thread(r);[/align][align=left] t.setPriority(Thread.MIN_PRIORITY);[/align][align=left] return t;[/align][align=left] }[/align]}

5.3[/u]启动带有属性设置的线程[/u][/u]ExecFromFactory.java[/u]

[align=left]package com.zj.concurrency.executors;[/align][align=left]import java.util.concurrent.ExecutorService;[/align][align=left]import java.util.concurrent.Executors;[/align][align=left]import com.zj.concurrency.executors.factory.DaemonThreadFactory;[/align][align=left]import com.zj.concurrency.executors.factory.MaxPriorityThreadFactory;[/align][align=left]import com.zj.concurrency.executors.factory.MinPriorityThreadFactory;[/align][align=left] [/align][align=left]public class ExecFromFactory {[/align][align=left] public static void main(String[] args) throws Exception {[/align][align=left] ExecutorService defaultExec = Executors.newCachedThreadPool();[/align][align=left] ExecutorService daemonExec = Executors[/align][align=left] .newCachedThreadPool(new DaemonThreadFactory());[/align][align=left] ExecutorService maxPriorityExec = Executors[/align][align=left] .newCachedThreadPool(new MaxPriorityThreadFactory());[/align][align=left] ExecutorService minPriorityExec = Executors[/align][align=left] .newCachedThreadPool(new MinPriorityThreadFactory());[/align][align=left] for (int i = 0; i < 10; i++)[/align][align=left] daemonExec.execute(new MyThread(i));[/align][align=left] for (int i = 10; i < 20; i++)[/align][align=left] if (i == 10)[/align][align=left] maxPriorityExec.execute(new MyThread(i));[/align][align=left] else if (i == 11)[/align][align=left] minPriorityExec.execute(new MyThread(i));[/align][align=left] else[/align][align=left] defaultExec.execute(new MyThread(i));[/align][align=left] }[/align]}

结果：[align=left]Create Thread-0[/align][align=left]Create Thread-1[/align][align=left]Create Thread-2[/align][align=left]Create Thread-3[/align][align=left]Thread-0 run 1 time(s)[/align][align=left]Thread-0 run 2 time(s)[/align][align=left]Thread-1 run 1 time(s)[/align][align=left]Thread-1 run 2 time(s)[/align][align=left]Thread-2 run 1 time(s)[/align][align=left]Thread-2 run 2 time(s)[/align][align=left]Create Thread-4[/align][align=left]Thread-4 run 1 time(s)[/align][align=left]Thread-4 run 2 time(s)[/align][align=left]Create Thread-5[/align][align=left]Thread-5 run 1 time(s)[/align][align=left]Thread-5 run 2 time(s)[/align][align=left]Create Thread-6[/align][align=left]Create Thread-7[/align][align=left]Thread-7 run 1 time(s)[/align][align=left]Thread-7 run 2 time(s)[/align][align=left]Create Thread-8[/align][align=left]Thread-8 run 1 time(s)[/align][align=left]Thread-8 run 2 time(s)[/align][align=left]Create Thread-9[/align][align=left]Create Thread-10[/align][align=left]Thread-10 run 1 time(s)[/align][align=left]Thread-10 run 2 time(s)[/align][align=left]Create Thread-11[/align][align=left]Thread-9 run 1 time(s)[/align][align=left]Thread-9 run 2 time(s)[/align][align=left]Thread-6 run 1 time(s)[/align][align=left]Thread-6 run 2 time(s)[/align][align=left]Thread-3 run 1 time(s)[/align][align=left]Thread-3 run 2 time(s)[/align][align=left]Create Thread-12[/align][align=left]Create Thread-13[/align][align=left]Create Thread-14[/align][align=left]Thread-12 run 1 time(s)[/align][align=left]Thread-12 run 2 time(s)[/align][align=left]Thread-13 run 1 time(s)[/align][align=left]Thread-13 run 2 time(s)[/align][align=left]Create Thread-15[/align][align=left]Thread-15 run 1 time(s)[/align][align=left]Thread-15 run 2 time(s)[/align][align=left]Create Thread-16[/align][align=left]Thread-16 run 1 time(s)[/align][align=left]Thread-16 run 2 time(s)[/align][align=left]Create Thread-17[/align][align=left]Create Thread-18[/align][align=left]Create Thread-19[/align][align=left]Thread-14 run 1 time(s)[/align][align=left]Thread-14 run 2 time(s)[/align][align=left]Thread-17 run 1 time(s)[/align][align=left]Thread-17 run 2 time(s)[/align][align=left]Thread-18 run 1 time(s)[/align][align=left]Thread-18 run 2 time(s)[/align][align=left]Thread-19 run 1 time(s)[/align][align=left]Thread-19 run 2 time(s)[/align][align=left]Thread-11 run 1 time(s)[/align][align=left]Thread-11 run 2 time(s)[/align]