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使用Executors创建和管理线程


[url]http://zhangjunhd.blog.51cto.com/113473/70068[b]1. 类 Executors[/b]
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。



[b]2. 接口 ThreadFactory[/b]


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);
   }
 }



[b]3. 接口ExecutorService[/b]


该接口提供了管理终止的方法。



[b]4.创建标准线程池启动线程[/b]


[color=red]4.1 提供一个简单的实现Runnable接口的线程[/color]


MyThread.java


package 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。



[color=red]4.2使用CachedThreadPool启动线程[/color]


CachedThreadPool.java


package 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-0


Create Thread-1


Create Thread-2


Create Thread-3


Thread-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-4


Thread-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.java


package 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-0


Create Thread-1


Create Thread-2


Create Thread-3


Create Thread-4


Thread-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.java


package 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-0


Create Thread-1


Create Thread-2


Create Thread-3


Create Thread-4


Thread-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)



[b]5.配合ThreadFactory接口的使用[/b]


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.java


package 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.java


package 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.java


package 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.java


package 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-0


Create Thread-1


Create Thread-2


Create Thread-3


Thread-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-4


Thread-4 run 1 time(s)


Thread-4 run 2 time(s)


Create Thread-5


Thread-5 run 1 time(s)


Thread-5 run 2 time(s)


Create Thread-6


Create Thread-7


Thread-7 run 1 time(s)


Thread-7 run 2 time(s)


Create Thread-8


Thread-8 run 1 time(s)


Thread-8 run 2 time(s)


Create Thread-9


Create Thread-10


Thread-10 run 1 time(s)


Thread-10 run 2 time(s)


Create Thread-11


Thread-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-12


Create Thread-13


Create Thread-14


Thread-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-15


Thread-15 run 1 time(s)


Thread-15 run 2 time(s)


Create Thread-16


Thread-16 run 1 time(s)


Thread-16 run 2 time(s)


Create Thread-17


Create Thread-18


Create Thread-19


Thread-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)


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