Thread pool implementation: semaphores can also be understood as small waiting queues

Preface

Manually implement a queue

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Code implementation ：

package com.cmsweety.demo;

import java.util.Random;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;

/**
 * @program: app
 * @description:  Semaphore usage 
 * @author: Zhaocunwei
 * @create: 2022-06-27 11:11
 **/

public class Demo { 
    
    /**
     *  Creating a thread pool 
     */
    public static void useSem