java - ExecutorService 固定线程拒绝

Question

我的某些线程有问题。

我的脚本

1 - 从文本文件将超过 1000 万行加载到 Array 中

2 - 创建一个包含 5 个固定线程的 ExecutorPool

3 - 然后它迭代该列表并向队列添加一些线程

executor.submit(new MyCustomThread(line,threadTimeout,"[THREAD "+Integer.toString(increment)+"]"));

现在 Activity 线程永远不会绕过 5 个固定线程，这很好，但我观察到我的处理器进入 100% 负载，并且我进行了一些调试，我看到 MyCustomThread 构造函数是被调用意味着无论我声明 5 个固定线程，ExecutorService 仍会尝试创建 1000 万个对象。

主要问题是:我该如何防止这种情况？我只是想让线程在没有空间的情况下被拒绝，而不是创建 1000 万个对象并一一运行它们。

第二个问题:如何获取当前的 Activity 线程？我尝试了 threadGroup.activeCount() 但它总是给我 5 5 5 5 ....

调用者类别:

System.out.println("Starting threads ...");
final ThreadGroup threadGroup = new ThreadGroup("workers");
//ExecutorService executor = Executors.newFixedThreadPool(howManyThreads);

ExecutorService executor = Executors.newFixedThreadPool(5,new ThreadFactory() {
    public Thread newThread(Runnable r) {
        return new Thread(threadGroup, r);
    }
});

int increment = 0;              
for(String line : arrayOfLines)
{
    if(increment > 10000)
    {
        //System.out.println("TOO MANY!!");
        //System.exit(0);
    }

    System.out.println(line);
    System.out.println(threadGroup.activeCount());

    if(threadGroup.activeCount() >= 5)
    {
        for(int i = 0; i < 10; i++)
        {
            System.out.println(threadGroup.activeCount());
            System.out.println(threadGroup.activeGroupCount());
            Thread.sleep(1000);
        }
    }


    try
    {
        executor.submit(new MyCustomThread(line,threadTimeout,"[THREAD "+Integer.toString(increment)+"]"));
    }
    catch(Exception ex)
    {
        continue;
        //System.exit(0);
    }

    increment++;
}

executor.awaitTermination(10, TimeUnit.MILLISECONDS);
executor.shutdown();

线程类别:

public class MyCustomThread extends Thread
{
    private String ip;
    private String threadName;
    private int threadTimeout = 10;

    public MyCustomThread(String ip)
    {
        this.ip = ip;
    }

    public MyCustomThread(String ip,int threadTimeout,String threadName)
    {

        this.ip = ip;
        this.threadTimeout = threadTimeout;
        this.threadName = threadName;

        System.out.prinln("MyCustomThread constructor has been called!");
    }

    @Override
    public void run()
    {
        // do some stuff that takes time ....
    }
}

谢谢。

Answer 1

你这样做有点不对。执行器的理念是将工作单元实现为 Runnable 或 Callable(而不是线程)。每个 Runnable 或 Callable 应该执行一项与其他 Runnable 或 Callable 互斥的原子工作。

执行器服务在内部使用线程池，因此您创建线程组和线程没有任何好处。

尝试这个简单的作品:

ExecutorService executor = Executors.newFixedThreadPool(5);`
executor.execute(new MyRunnableWorker());

public class MyRunnableWorker implements Runnable{
    private String ip;
    private String threadName;
    private int threadTimeout = 10;

    public MyRunnableWorker(String ip){
        this.ip = ip;
    }

    public MyRunnableWorker(String ip,int threadTimeout,String threadName){
        this.ip = ip;
        this.threadTimeout = threadTimeout;
        this.threadName = threadName;

        System.out.prinln("MyRunnableWorker constructor has been called!");
    }

    @Override
    public void run(){    {
        // do some stuff that takes time ....
    }
}

这会给你你想要的。还可以尝试使用 VisualVM 测试线程代码执行，以查看线程如何运行以及负载分布。