测试代码如下：
public class Task implements Runnable {
private int no;
private int size;
public Task(int no, int size) {
this.no = no;
this.size = size;
}
@Override
public void run() {
try {
System.out.println("执行中, Task: " + no + ", Thread: " + Thread.currentThread().getName() + ", queue.size: " + size);
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
public class Main {
private static ExecutorService pool;
public static void main(String[] args) {
BlockingQueue queue = new ArrayBlockingQueue(8);
pool = new ThreadPoolExecutor(
2,
5,
1000,
TimeUnit.MILLISECONDS,
queue,
Executors.defaultThreadFactory(),
new RejectedExecutionHandler() {
@Override
public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) {
System.out.println("拒绝中, " + r.toString() + ", queue.size: " + queue.size());
}
});
for (int i = 0; i
JDK 8 环境下的运行结果：
执行中, Task: 1, Thread: pool-1-thread-2, queue.size: 0
执行中, Task: 10, Thread: pool-1-thread-3, queue.size: 8
执行中, Task: 11, Thread: pool-1-thread-4, queue.size: 8
执行中, Task: 12, Thread: pool-1-thread-5, queue.size: 8
执行中, Task: 0, Thread: pool-1-thread-1, queue.size: 0
拒绝中, [email protected], queue.size: 8
拒绝中, [email protected], queue.size: 8
执行中, Task: 2, Thread: pool-1-thread-4, queue.size: 0
执行中, Task: 3, Thread: pool-1-thread-3, queue.size: 1
执行中, Task: 4, Thread: pool-1-thread-1, queue.size: 2
执行中, Task: 5, Thread: pool-1-thread-2, queue.size: 3
执行中, Task: 6, Thread: pool-1-thread-5, queue.size: 4
执行中, Task: 7, Thread: pool-1-thread-4, queue.size: 5
执行中, Task: 9, Thread: pool-1-thread-3, queue.size: 7
执行中, Task: 8, Thread: pool-1-thread-1, queue.size: 6
JDK 17 环境下的运行结果：
拒绝中, [email protected], queue.size: 8
拒绝中, [email protected], queue.size: 8
执行中, Task: 11, Thread: pool-1-thread-4, queue.size: 8
执行中, Task: 10, Thread: pool-1-thread-3, queue.size: 8
执行中, Task: 12, Thread: pool-1-thread-5, queue.size: 8
执行中, Task: 0, Thread: pool-1-thread-1, queue.size: 0
执行中, Task: 1, Thread: pool-1-thread-2, queue.size: 0
执行中, Task: 3, Thread: pool-1-thread-4, queue.size: 1
执行中, Task: 2, Thread: pool-1-thread-3, queue.size: 0
执行中, Task: 4, Thread: pool-1-thread-5, queue.size: 2
执行中, Task: 5, Thread: pool-1-thread-2, queue.size: 3
执行中, Task: 6, Thread: pool-1-thread-1, queue.size: 4
执行中, Task: 7, Thread: pool-1-thread-4, queue.size: 5
执行中, Task: 8, Thread: pool-1-thread-3, queue.size: 6
执行中, Task: 9, Thread: pool-1-thread-2, queue.size: 7
结论
可见 JDK17 的 ThreadPoolExecutor ，在通过 execut 提交 runnable 后，不会立即执行被提交的 runnable ，而是等待一段时间。如果在这段等待时间内没有新的 runnable 提交，才开始执行。
