了解 ThreadPoolExecutor 内部工作

Question

我有以下代码：

public class ExecFramework implements Runnable {
int i;

public ExecFramework() {

}

public ExecFramework(int i) {
    this.i = i;
}

public void run() {
    System.out.println(Thread.currentThread().getName() + " " + i);
    try {
        Thread.sleep(10);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
}

public static void main(String[] args) {

    ExecutorService pool=new ThreadPoolExecutor(2, 10, 5000,TimeUnit.SECONDS, new ArrayBlockingQueue(2));
    for (int i = 0; i < 20; i++) {
        Runnable obj=new ExecFramework(i);
        pool.execute(obj);
    }
    pool.shutdown();
    while(pool.isTerminated()){
        System.out.println("ExecutorService is terminated");
    }

}

}

我对 ThreadPoolExecutor 工作方式的了解是否正确：

1. 如果 NumberOfThreadRunning
2. 如果 NumberOfThreadRunning > CoreNumberOfThreads 然后将此任务排队在 BlockingQueue 但如果队列已满则仅在以下情况下创建一个新线程 NumberOfThread
3. 任务完成后，运行该任务的线程可用于其他任务。

根据第三点。我应该能够使用 ThreadPoolExecutor 执行 20 个任务。

为什么上面代码的输出是？

pool-1-thread-5 6
pool-1-thread-4 5
pool-1-thread-3 4
pool-1-thread-1 0
pool-1-thread-2 1
pool-1-thread-6 7
pool-1-thread-7 8
pool-1-thread-8 9
pool-1-thread-9 10
pool-1-thread-10 11
Exception in thread "main" java.util.concurrent.RejectedExecutionException: Task executionFramework.ExecFramework@232204a1 rejected from java.util.concurrent.ThreadPoolExecutor@4aa298b7[Running, pool size = 10, active threads = 10, queued tasks = 2, completed tasks = 0]
	at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:2063)
	at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:830)
	at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1379)
	at executionFramework.ExecFramework.main(ExecFramework.java:88)
pool-1-thread-8 2
pool-1-thread-6 3

Answer 1

文档说：https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ThreadPoolExecutor.html

在拒绝的任务部分。

在你的情况下，我猜这个：

当 Executor 对最大线程和工作队列容量都使用有限界限，并且已经饱和时

发生了。