java线程池小例子

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最近一直在研究线程池的使用方法，具体线程池工作原理可以参照前几天写的模拟线程池的例子 java线程池实现方式 java已经有实现好的线程池，并且有完善的管理机制，下面将最近学习体会分享一下。

首先创建一个监控线程来监控线程池的具体资源情况

/**
* 监控线程
* @author lizh
* @date 2014-1-26下午3:57:57
* @fileName MonitorThread.java
* @package threadPoolJava
* @project Test
*/
public class MonitorThread implements Runnable{
   private int delay;//线程监控周期
   private ThreadPoolExecutor executor;//线程池
   private boolean isRun = true;//监控线程是否运行
   public MonitorThread(int delay, ThreadPoolExecutor executor) {
       this.delay = delay;
       this.executor = executor;
   }
   public void shutDown(){
       this.isRun = false;
   }

   @Override
   public void run() {
       while(isRun){
           System.out.println(
                        String.format("[monitor] [%d/%d] Active: %d, Completed: %d, Task: %d, isShutdown: %s, isTerminated: %s",
                            this.executor.getPoolSize(),
                            this.executor.getCorePoolSize(),
                            this.executor.getActiveCount(),
                            this.executor.getTaskCount(),
                            this.executor.getCompletedTaskCount(),
                            this.executor.isShutdown(),
                            this.executor.isTerminated()));
                    try {
                        Thread.sleep(delay*1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
       }
   }

}

创建当任务被拒绝后的处理

/**
* 处理被线程池拒绝的任务
* @author lizh
* @date 2014-1-26下午3:57:33
* @fileName RejectedExecutionHandlerImpl.java
* @package threadPoolJava
* @project Test
*/
public class RejectedExecutionHandlerImpl implements RejectedExecutionHandler{

   @Override
   public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) {
       System.out.println(r.toString()+"is rejected");
       while(executor.getQueue().size()>=5){
           try {
               Thread.sleep(1000);
           } catch (InterruptedException e) {
               e.printStackTrace();
           }
       }
       executor.execute(r);
       // 此处可以使用主线程直接将被拒绝的work执行，也可以由上述代码等线程的任务队列小于最大值时重新添加到线程池
//       Thread t = new Thread(r);
//       t.start();
   }

}

下面创建任务线程测试类

/**
* 工作线程
* @author lizh
* @date 2014-1-26下午4:01:57
* @fileName WorkThread.java
* @package threadPoolJava
* @project Test
*/
public class WorkThread implements Runnable{
   private String command;

   public WorkThread(String command) {
       this.command = command;
   }

   @Override
   public void run() {
       System.out.println(Thread.currentThread().getName()+"strat");
       processCommand();
       System.out.println(Thread.currentThread().getName()+"end");
   }
   public void processCommand(){
       try {
           Thread.sleep(5000);
       } catch (InterruptedException e) {
           e.printStackTrace();
       }
   }

   @Override
   public String toString() {
       return "WorkThread [command=" + command + "]";
   }


}

最后创建模拟线程池实用类

/**
* 测试线程池类
* @author lizh
* @date 2014-1-26下午4:01:29
* @fileName WorkPool.java
* @package threadPoolJava
* @project Test
*/
public class WorkPool {
   public static void main(String[] args) {
       RejectedExecutionHandler rejeHandler = new RejectedExecutionHandlerImpl();
       ThreadFactory threadFaction = Executors.defaultThreadFactory();
       ThreadPoolExecutor pool = new ThreadPoolExecutor(2, 4, 10,
               TimeUnit.SECONDS, new ArrayBlockingQueue<Runnable>(5),
               threadFaction, rejeHandler);
       MonitorThread monitor = new MonitorThread(3, pool);
       Thread thread = new Thread(monitor);
       thread.start();
       for (int i = 0; i < 20; i++) {
           WorkThread th = new WorkThread("cmd" + i);
           pool.execute(th);
       }
       try {
           Thread.sleep(7000);
       } catch (InterruptedException e) {
           e.printStackTrace();
       }
       pool.execute(new WorkThread("123"));
        pool.shutdown();
        try {
           Thread.sleep(10000);
       } catch (InterruptedException e) {
           e.printStackTrace();
       }
        monitor.shutDown();
   }
}

很简单的小例子运行起来结果如下

相信看完大家都会明白尽管任务队列最大为5 允许最大线程数为4 但是21个任务都成功执行很神奇一起分享

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