1、无论任务是从run中正常返回，还是抛出一个异常而返回，afterExecute都会被调用。如果任务在完成后带有一个Error，那么就不会盗用afterExecute。

2、如果beforeExecute抛出一个RuntimeException，那么任务将不被执行，并且afterExecute也不会被调用。

3、在线程完成关闭操作时调用terminated，也就是在所有任务都已经完成并且所有工作者线程也已经关闭后。terminated可以用来释放Executor在其生命周期里分配的各种资源，此外还可以执行发送通知、记录日志或者手机finalize统计信息等操作。

4、代码示例如下：

/**
 * TimingThreadPool
 * <p/>
 * Thread pool extended with logging and timing
 *
 * @author Brian Goetz and Tim Peierls
 */
public class TimingThreadPool extends ThreadPoolExecutor {

    public TimingThreadPool() {
        super(1, 1, 0L, TimeUnit.SECONDS, null);
    }

    private final ThreadLocal<Long> startTime = new ThreadLocal<Long>();
    private final Logger log = Logger.getLogger("TimingThreadPool");
    private final AtomicLong numTasks = new AtomicLong();
    private final AtomicLong totalTime = new AtomicLong();

    @Override
    protected void beforeExecute(Thread t, Runnable r) {
        super.beforeExecute(t, r);
        log.fine(String.format("Thread %s: start %s", t, r));
        startTime.set(System.nanoTime());
    }

    @Override
    protected void afterExecute(Runnable r, Throwable t) {
        try {
            long endTime = System.nanoTime();
            long taskTime = endTime - startTime.get();
            numTasks.incrementAndGet();
            totalTime.addAndGet(taskTime);
            log.fine(String.format("Thread %s: end %s, time=%dns",
                    t, r, taskTime));
        } finally {
            super.afterExecute(r, t);
        }
    }

    @Override
    protected void terminated() {
        try {
            log.info(String.format("Terminated: avg time=%dns",
                    totalTime.get() / numTasks.get()));
        } finally {
            super.terminated();
        }
    }
}