带你读《2022技术人的百宝黑皮书》——合理使用线程池以及线程变量（5）

  /**
* Same as a java.util.concurrent.ThreadPoolExecutor but implements a much more efficient
* {@link #getSubmittedCount()} method, to be used to properly handle the work queue.
* If a RejectedExecutionHandler is not specified a default one will be configured
* and that one will always throw a RejectedExecutionException 6 *
  */
  public class ThreadPoolExecutor extends java.util.concurrent.ThreadPoolExecutor { 9
/**
*The number of tasks submitted but not yet finished. This includes tasks
*in the queue and tasks that have been handed to a worker thread but the
*latter did not start executing the task yet.
*This number is always greater or equal to {@link #getActiveCount()}.
*/
// 新增的submittedCount成员变量，用于统计已提交但还未完成的任务数private final AtomicInteger submittedCount = new AtomicInteger(0); private final AtomicLong lastContextStoppedTime = new AtomicLong(0L);
// 构造函数
public ThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, ThreadFactory threadFactory,
RejectedExecutionHandler handler) {
super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory, handler);
// 预启动所有核心线程prestartAllCoreThreads();
}

@Override
public void execute(Runnable command) { execute(command,0,TimeUnit.MILLISECONDS);
}
public void execute(Runnable command, long timeout, TimeUnit unit) { submittedCount.incrementAndGet();
try {
super.execute(command);
} catch (RejectedExecutionException rx) {
if (super.getQueue() instanceof TaskQueue) {
final TaskQueue queue = (TaskQueue)super.getQueue(); try {
if (!queue.force(command, timeout, unit)) { submittedCount.decrementAndGet();
throw new RejectedExecutionException("Queue capacity is full.");
}
} catch (InterruptedException x) { submittedCount.decrementAndGet();    throw new RejectedExecutionException(x);
}
} else {
submittedCount.decrementAndGet(); throw rx;
}