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通过阅读线程池,我感到非常困惑。我了解了这个概念,它们实际上是如何工作的。但我在这部分感到困惑,如何编码。

我在网上搜索了很多。最后我得到了一个博客,上面有代码,如下所示,

条件是,不使用内置类

代码 1

public class ThreadPool {

  private BlockingQueue taskQueue = null;
  private List<PoolThread> threads = new ArrayList<PoolThread>();
  private boolean isStopped = false;

  public ThreadPool(int noOfThreads, int maxNoOfTasks){
    taskQueue = new BlockingQueue(maxNoOfTasks);

    for(int i=0; i<noOfThreads; i++){
      threads.add(new PoolThread(taskQueue));
    }
    for(PoolThread thread : threads){
      thread.start();
    }
  }

  public void synchronized execute(Runnable task){
    if(this.isStopped) throw
      new IllegalStateException("ThreadPool is stopped");

    this.taskQueue.enqueue(task);
  }

  public synchronized void stop(){
    this.isStopped = true;
    for(PoolThread thread : threads){
      thread.stop();
    }
  }

}

代码 2

public class PoolThread extends Thread {
  private BlockingQueue taskQueue = null;
  private boolean       isStopped = false;
  public PoolThread(BlockingQueue queue){
    taskQueue = queue;
  }
  public void run(){
    while(!isStopped()){
      try{
        Runnable runnable = (Runnable) taskQueue.dequeue();
        runnable.run();
      } catch(Exception e){
        //log or otherwise report exception,
        //but keep pool thread alive.
      }
    }
  }
  public synchronized void stop(){
    isStopped = true;
    this.interrupt(); //break pool thread out of dequeue() call.
  }
  public synchronized void isStopped(){
    return isStopped;
  }
}

代码 3:-

public class BlockingQueue {

  private List queue = new LinkedList();
  private int  limit = 10;

  public BlockingQueue(int limit){
    this.limit = limit;
  }

  public synchronized void enqueue(Object item)
  throws InterruptedException  {
    while(this.queue.size() == this.limit) {
      wait();
    }
    if(this.queue.size() == 0) {
      notifyAll();
    }
    this.queue.add(item);
  }

  public synchronized Object dequeue()
  throws InterruptedException{
    while(this.queue.size() == 0){
      wait();
    }
    if(this.queue.size() == this.limit){
      notifyAll();
    }

    return this.queue.remove(0);
  }    
}

我试图理解这段代码的作用。但我不明白这段代码的流程。你能帮我理解这段代码吗?

Mainly I have problems in **Code 2 :- run method**

Why execute method's argument are of Runnable type?

How input array given to this code??

帮我。

提前致谢。

4

2 回答 2

2
  public void run(){
    while(!isStopped()){

循环直到线程池停止。

      try{
        Runnable runnable = (Runnable) taskQueue.dequeue();

从任务队列中拉出头任务。

        runnable.run();

运行任务。

      } catch(Exception e){
        //log or otherwise report exception,
        //but keep pool thread alive.

如果任务抛出异常,不要做任何特别的事情,只是不要传递它。

      }
    }
  }
于 2013-01-22T13:20:36.427 回答
1

编辑:

我现在明白这是一个班级项目,但我会把我的答案留给后代。

如果您尝试在 Java 下使用线程池,那么这些类已经为您实现了所有这些java.util.concurrent.*。其他答案解决并解释您的特定代码。

例如,这是您需要使用ExecutorService代码设置线程池的内容。在盖子下面ExecutorService处理线程并使用LinkedBlockingQueue. 您定义MyJob实现“可运行”的类并执行池中线程运行的工作。根据您的需要,它可以是短期或长期运行的任务。

// create a thread pool with 10 workers
ExecutorService threadPool = Executors.newFixedThreadPool(10);
// or you can create an open-ended thread pool
// ExecutorService threadPool = Executors.newCachedThreadPool();
// define your jobs somehow
for (MyJob job : jobsToDo) {
    threadPool.submit(job);
}
// once we have submitted all jobs to the thread pool, it should be shutdown
threadPool.shutdown();
...
public class MyJob implements Runnable {
    // you can construct your jobs and pass in context for them if necessary
    public MyJob(String someContext) {
        ...
    }
    public void run() {
        // process the job
    }
}
于 2013-01-22T13:20:09.630 回答