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Java:使用Executors创建和管理线程

2017-08-21 13:45 579 查看

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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.java

[align=left]package com.zj.concurrency.executors;[/align]
[align=left] [/align]
public class MyThread implements Runnable
{
    private int count =
1, number;
[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]
           System.out.println("Thread-" + number + "
run " + count+" time(s)");
[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使用CachedThreadPool启动线程
CachedThreadPool.java

[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]
    public static void main(String[]
args) {
[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]
}

[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]
    public static void main(String[]
args) {
[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]
}

[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]
    public static void main(String[]
args) {
[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]
}

[align=left]package com.zj.concurrency.executors.factory;[/align]
[align=left]import java.util.concurrent.ThreadFactory;[/align]
[align=left] [/align]
public class DaemonThreadFactory implements ThreadFactory
{
[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]
}

5.2 设置优先级属性
最高优先级MaxPriorityThreadFactory.java

[align=left]package com.zj.concurrency.executors.factory;[/align]
[align=left]import java.util.concurrent.ThreadFactory;[/align]
[align=left] [/align]
public class MaxPriorityThreadFactory implements ThreadFactory
{
[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MinPriorityThreadFactory.java

[align=left]package com.zj.concurrency.executors.factory;[/align]
[align=left]import java.util.concurrent.ThreadFactory;[/align]
[align=left] [/align]
public class MinPriorityThreadFactory implements ThreadFactor
cea6
y
{
[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启动带有属性设置的线程
ExecFromFactory.java

[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]
    public static void main(String[]
args) throws Exception {
[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]
       for (int i = 0; i < 10;
i++)
[align=left]           daemonExec.execute(new MyThread(i));[/align]
       for (int i = 10; i < 20;
i++)
[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]

本文出自 “i张俊” 博客，请务必保留此出处http://zhangjunhd.blog.51cto.com/113473/70068

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