线程池参数调优「建议收藏」

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ThreadPoolExecutor

ThreadPoolExecutor构造函数的五大参数

 public ThreadPoolExecutor(int corePoolSize,
                              int maximumPoolSize,
                              long keepAliveTime,
                              TimeUnit unit,
                              BlockingQueue<Runnable> workQueue) { 
   
        this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
             Executors.defaultThreadFactory(), defaultHandler);
    }

corePoolSize 核心线程数，表示线程池支持的最小线程数
maximumPoolSize 最大线程数，当线程数大于核心线程数后，并且有界队列里存放能时，线程池还能接受maximumPoolSize – corePoolSize个线程
keepAliveTime 保持存活时间，空闲线程的存活时间，为了更好的复用线程
unit 线程存活时间的单位
workQueue 队列，等待线程存放的队列

提问：如下线程池同一时间最多能接受多少个线程？

 ThreadPoolExecutor pool = new ThreadPoolExecutor(2,5,10L, TimeUnit.SECONDS,new ArrayBlockingQueue<>(5));

答案是10个，等待队列里5个，最大线程数5个，多的线程请求将会被拒绝，异常如下

线程池的处理流程：

逻辑流程图

写个demo压测下线程池

public class ThreadPoolDemo { 
   

    public static void main(String[] args) { 
   

        ThreadPoolExecutor pool = new ThreadPoolExecutor(80,150,10L, TimeUnit.SECONDS,new ArrayBlockingQueue<>(200));
        long start = System.currentTimeMillis() / 1000;
        IntStream.range(0,500).forEach(i ->{ 
   
            pool.submit(new MyThread());
            try { 
   
                Thread.sleep(3L);
            } catch (InterruptedException e) { 
   
                e.printStackTrace();
            }
        });
        pool.shutdown();
        System.out.println("use time " + (System.currentTimeMillis() / 1000 - start) + "秒");

    }

   static class MyThread implements Runnable{ 
   

       @Override
        public void run() { 
   
            try { 
   
                Thread.sleep(500L);
                System.out.println(Thread.currentThread().getName()+" run ....");
            } catch (InterruptedException e) { 
   
                e.printStackTrace();
            }
        }
    }
}