After using the thread pool, the main thread cannot end

package com.fwkily.practice.threadpool;

import java.util.concurrent.*;

/**
 * @Author: fuwk
 * @Description:
 * @Date: 18:08 2022/1/6
 */
public class Test {

    public static void main(String[] args) {
        final ExecutorService EXECUTOR_BILL = new ThreadPoolExecutor(Runtime.getRuntime().availableProcessors() * 2, Integer.MAX_VALUE,
                0, TimeUnit.MILLISECONDS, new SynchronousQueue<>(), new ThreadPoolExecutor.CallerRunsPolicy());

        CompletionService<Boolean> completionService = new ExecutorCompletionService<>(EXECUTOR_BILL);
        CountDownLatch countDownLatch = new CountDownLatch(10);
        for (int i = 0; i < 10; i++) {
            int finalI = i;
            completionService.submit(() -> { 
                new Thread(() -> System.out.println("thread" + finalI + "execution task"),"thread" + finalI).start(); 
                try { 
                    Thread.sleep (1000); 
                } catch (InterruptedException e) { 
                    e.printStackTrace(); 
                }finally { 
                    countDownLatch.countDown(); 
                } 
                return true; 
            }); 
        } 
        for (int i = 0; i < 10; i++) { 
            try { 
                Boolean aBoolean = completionService.take().get();
                System.out.println("return result" + aBoolean); 
            } catch (InterruptedException | ExecutionException e) {
                e.printStackTrace(); 
            } 
        } 
        System.out.println("Tasks are ready!"); 
        try { 
            countDownLatch.await(); 
        } catch (InterruptedException e) { 
            e.printStackTrace(); 
        } 
        System.out.println( "This is the main thread to perform the following tasks!"); 
        //Exit the thread pool --- be sure to shutdown the thread pool, otherwise the main thread will not end 
        EXECUTOR_BILL.shutdown(); 
    } 

} 

The main thread has not ended

 

Join shutdown, exit the thread pool, the main thread has ended