我正在尝试理解
ThreadPoolExecutor
中队列的行为。在下面的程序中,当我使用LinkedBlockingQueue
时,我只能一次向线程池提交一个任务。但是如果我用SynchronousQueue
代替LinkedBlockingQueue
,我可以立即将所有5个任务提交到池中。在这种情况下,SynchronousQueue
与LinkedBlockingQueue
有何不同?
Java程序:
import java.util.concurrent.Executors;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.SynchronousQueue;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
public class Sample {
public static void main(String[] args) throws InterruptedException {
LinkedBlockingQueue<Runnable> threadPoolQueue = new LinkedBlockingQueue<>();
// SynchronousQueue<Runnable> threadPoolQueue = new SynchronousQueue<>();
ThreadFactory threadFactory = Executors.defaultThreadFactory();
ThreadPoolExecutor tpe = new ThreadPoolExecutor(0, Integer.MAX_VALUE, 60L, TimeUnit.SECONDS, threadPoolQueue, threadFactory);
Runnable np;
for (int i = 1; i <= 5; i++) {
np = new SampleWorker("ThreadPoolWorker " + i);
tpe.submit(np);
}
System.out.println(tpe.getCorePoolSize());
System.out.println(tpe.getPoolSize());
System.out.println(tpe.getActiveCount());
tpe.awaitTermination(Long.MAX_VALUE, TimeUnit.MILLISECONDS);
tpe.shutdown();
System.out.println("Main task finished");
}
}
class SampleWorker implements Runnable {
private String workerName;
SampleWorker(String tName) {
workerName = tName;
}
@Override
public void run() {
try {
for (int i = 1; i <= 10; i++) {
Thread.sleep(3000);
System.out.println(this.workerName);
}
System.out.println(this.workerName + " finished");
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
SynchronousQueue
和LinkedBlockingQueue
(大小为1)之间的区别。但是在这里,我没有为任何一个队列指定大小。使用LinkedBlockingQueue
,我一次只能提交一个任务,而使用SynchronousQueue
,我可以同时提交所有5个任务。在两种情况下,我都将corePoolSize
设置为0。那么corePoolSize
不会影响SynchronousQueue
吗? - UnahDcorePoolSize
不影响底层的BlockingQueue
,它仅控制ThreadPoolExecutor
的线程池大小,而不是BlockingQueue
的大小。并且,正如文档所说,SynchronousQueue
没有任何内部容量,甚至没有一个容量,size()
也始终返回零。 - Maxim Ponomarev