使用Executors创建和管理线程

于 2010-08-17 16:07:00 发布
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分类专栏： JAVA 文章标签： thread class string exception 任务
本文详细介绍了Java中线程池的几种类型及其使用方法，包括newCachedThreadPool、newFixedThreadPool和newSingleThreadExecutor等，并展示了如何通过ThreadFactory自定义线程属性。

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newCachedThreadPool建立可以快取的Thread，每个Thread预设可idle 60秒
newFixedThreadPool包括固定数量的Thread
newSingleThreadExecutor 只有一个Thread，循序的执行指定给它的每个任务
 newScheduledThreadPool可排程的Thread
 newSingleThreadScheduledExecutor单一可排程的Thread

 

 example:

package onlyfun.caterpillar;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class ExecutorDemo { 
         public static void main(String[] args) {
                  ExecutorService service = Executors.newFixedThreadPool(5);
         for(int i = 0; i < 10; i++) {
              final int count = i;
             service.submit(new Runnable() {
                public void run() {
      System.out.println(count); 
       try {
          Thread.sleep(2000);
       } catch (InterruptedException e) {
           e.printStackTrace();
       }
                 }
             });  
                      }    
                   service.shutdown(); // 最后记得关闭Thread pool 
            }
}

 

 

---------------------------------------------------------------------------------------------------------------

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

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。
 
4.2使用CachedThreadPool启动线程
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)
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.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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