获得线程池中活跃的线程数

package org.thread;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadPoolExecutor;

/**
 * 获取线程池中活跃数
 */
public class ThreadActiveCount {

//    private static ExecutorService executorService = Executors.newFixedThreadPool(5);

    private static ExecutorService executorService = Executors.newCachedThreadPool();

    public static void main(String[] args) {
        ThreadActiveCount threadActiveCount = new ThreadActiveCount();
        int activeAcount = threadActiveCount.getActiveAcount();
        System.out.println(activeAcount);
        for (int i = 0; i < 100; i++) {
            executorService.submit(() -> {
                System.out.println("hello world");
            });
        }
        int activeAcount1 = threadActiveCount.getActiveAcount();
        System.out.println(activeAcount1);
    }

    public int getActiveAcount(){
        ThreadPoolExecutor threadPoolExecutor =(ThreadPoolExecutor) executorService;
        int activeCount = threadPoolExecutor.getActiveCount();
        return activeCount;
    }
}