如果出现异常，ThreadPoolExecutor::afterExecute 会返回 runnable 吗？答案

【问题标题】：Will ThreadPoolExecutor:: afterExecute return runnable in case of exception?如果出现异常，ThreadPoolExecutor::afterExecute 会返回 runnable 吗？
【发布时间】：2017-09-17 04:50:33
【问题描述】：

ThreadPoolExecutor 的 Javadoc 定义 (https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ThreadPoolExecutor.html#afterExecute(java.lang.Runnable,%20java.lang.Throwable))

protected void afterExecute(Runnable r, Throwable t)

如果发生异常，初始可运行对象是否会传递给函数？

【问题讨论】：

“runnable 被返回”是什么意思？
@Jesper 改写
是的，Runnable 被传递给afterExecute，以防Runnable 抛出异常； API 文档对此进行了解释。你究竟为什么怀疑它？你也可以自己试试看（创建一个扩展ThreadPoolExecutor的类，重写afterExecute方法，让它执行一个抛出异常的Runnable，并检查你的afterExecute是否按预期调用） .

标签： java threadpool threadpoolexecutor

【解决方案1】：

它被退回。很容易检查 - 考虑基于 doc 的代码：

public class MainApp {

    public static void main(String[] args) {
        testme();
    }

    public static void testme() {
        ThreadPoolExecutor myown = new ExtendedExecutor(2,4,10, TimeUnit.DAYS.SECONDS, new ArrayBlockingQueue<Runnable>(2));

        myown.execute(() -> {
                throw new RuntimeException("Something went wrong");
  //            System.out.println("Hey there");
        }
    );
}


static class ExtendedExecutor extends ThreadPoolExecutor {

    public ExtendedExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue) {
        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue);
    }

    protected void afterExecute(Runnable r, Throwable t) {
        super.afterExecute(r, t);
        if (t == null && r instanceof Future<?>) {
            try {
                Object result = ((Future<?>) r).get();
            } catch (CancellationException ce) {
                t = ce;
            } catch (ExecutionException ee) {
                t = ee.getCause();
            } catch (InterruptedException ie) {
                Thread.currentThread().interrupt(); // ignore/reset
            }
        }
        if (t != null) {
            System.out.println("We've got error");
            System.out.println(r==null?"null":"not null");
        }
    }
}

【讨论】：

帮我写这个程序的单元测试用例