使用Executors建立和管理執行緒

轉自: [url]http://blog.csdn.net/liuzhengkang/archive/2008/10/24/3137340.aspx[/url]
1. 類 Executors
此類中提供的一些方法有：
1.1 public static ExecutorService newCachedThreadPool()
建立一個可根據需要建立新執行緒的執行緒池，但是在以前構造的執行緒可用時將重用它們。對於執行很多短期非同步任務的程式而言，這些執行緒池通常可提高程式效能。

1.2 public static ExecutorService newFixedThreadPool(int nThreads)
建立一個可重用固定執行緒數的執行緒池，以共享的無界佇列方式來執行這些執行緒。

1.3 public static ExecutorService newSingleThreadExecutor()
建立一個使用單個 worker 執行緒的 Executor，以無界佇列方式來執行該執行緒。

這三個方法都可以配合介面ThreadFactory的例項一起使用。並且返回一個ExecutorService介面的例項。
2. 介面 ThreadFactory
根據需要建立新執行緒的物件。使用執行緒工廠就無需再手工編寫對 new Thread 的呼叫了，從而允許應用程式使用特殊的執行緒子類、屬性等等。
此介面最簡單的實現就是：

class SimpleThreadFactory implements ThreadFactory {
   public Thread newThread(Runnable r) {
     return new Thread(r);
   }
 }

3. 介面ExecutorService
該介面提供了管理終止的方法。
4.建立標準執行緒池啟動執行緒
4.1 提供一個簡單的實現Runnable介面的執行緒
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;
       }
    }
}

這個執行緒會列印出相應的建立和執行資訊。

4.2使用CachedThreadPool啟動執行緒
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();
    }
}

結果：
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啟動執行緒
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();
    }
}

結果：
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啟動執行緒
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();
    }
}

結果：
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)
5.配合ThreadFactory介面的使用
我們試圖給執行緒加入daemon和priority的屬性設定。
5.1設定後臺執行緒屬性
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 設定優先順序屬性
最高優先順序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;
    }
}

最低優先順序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啟動帶有屬性設定的執行緒
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));
    }
}

結果：
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)