Java Thread - 如何创建ThreadPoolExecutor并获取池大小

import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;


public class PoolSize {

    public static void main(String[] args) {
      ThreadPoolExecutor executor = new ThreadPoolExecutor(10, 20, 60L, TimeUnit.SECONDS, new LinkedBlockingQueue());
      System.out.println(executor.getPoolSize());
    }
}