如何获取 ExecutorService 当前活动的线程数

红太狼 2022-04-23 00:54 1130阅读 0赞

我们在做多线程的时候，想要查看下当前线程池有多少活动的线程，如何获取呢？

请看下面做的例子即可得到：

import java.util.concurrent.ExecutorService;
    import java.util.concurrent.Executors;
    import java.util.concurrent.ThreadPoolExecutor;
    
    /**
    * @Description 获取线程池中的当前活动线程
    * @Author Andy
    *@Date 2018/6/13
    */
    public class TestForExecutorServicePool {
    	public static void main(String[] args) {
    	
    		ExecutorService exes = null;
    		try{
    		
    			exes = Executors.newFixedThreadPool(10);
    			
    			//想线程池中放入三个任务
    			exes.execute(new Task());
    			exes.execute(new Task());
    			exes.execute(new Task());
    			Thread.sleep(500);//延迟500ms,因为三个任务放入需要时间
    			//将exes转换为ThreadPoolExecutor,ThreadPoolExecutor有方法 getActiveCount()可以得到当前活动线程数
    			int threadCount = ((ThreadPoolExecutor)exes).getActiveCount();
    			System.out.println("1.threadCount===="+threadCount);
    			Thread.sleep(3000);
    			
    			threadCount = ((ThreadPoolExecutor)exes).getActiveCount();
    			System.out.println("2.threadCount===="+threadCount);
    			
    			exes.execute(new Task());
    			exes.execute(new Task());
    			Thread.sleep(500);
    			
    			threadCount = ((ThreadPoolExecutor)exes).getActiveCount();
    			System.out.println("3.threadCount===="+threadCount);
    			
    		}catch(Exception e){
    			e.printStackTrace();
    		}finally{
    			if(exec!=null){
    				exes.shutdown();
    			}
    		}
    	}
    		
    }
    class Task implements Runnable{
    		@Override
    		public void run() {
    			try{
    				Thread.sleep(3000);
    			}catch(Exception e){
    				e.printStackTrace();
    			}
    		}
    
    }