自定义线程池

package com.koala.learn.charter4;

/**
 * @Description TODO
 * @Date 2022/2/28 0:04
 * @Created by koala
 */

public class Start3 {
    public static void main(String[] args) {
        DefaultThreadPool<HouseWork> pool = new DefaultThreadPool<>(2);
        pool.execute(new HouseWork(1000L,"dinner"));
        pool.execute(new HouseWork(1000L,"clear"));
        pool.execute(new HouseWork(1000L,"dish"));
        pool.execute(new HouseWork(1000L,"close window"));
    }
}

package com.koala.learn.charter4;

/**
 * @Description TODO
 * @Date 2022/2/27 21:25
 * @Created by koala
 */

public interface ThreadPool<Job extends Runnable> {
    // 执行一个工作
    void execute(Job job);

    void shutdown();

    void addWorker(int num);

    void removeWorker(int num);

    int getJobSize();
}

package com.koala.learn.charter4;

import lombok.SneakyThrows;

/**
 * @Description TODO
 * @Date 2022/2/28 0:05
 * @Created by koala
 */

public class HouseWork implements Runnable{

    private Long time;

    private String msg;

    public HouseWork(Long time, String msg) {
        this.time = time;
        this.msg = msg;
    }

    @SneakyThrows
    @Override
    public void run() {
        Thread.sleep(time);
        System.out.println("I will do " + msg + " it will waste " + time + " second");
    }
}

package com.koala.learn.charter4;

import java.util.ArrayList;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.atomic.AtomicLong;

/**
 * @Description TODO
 * @Date 2022/2/27 21:29
 * @Created by koala
 */

public class DefaultThreadPool<Job extends Runnable> implements ThreadPool<Job> {

    // 最大的工作人数
    public static final int MAX_WORKER_NUMBERS = 10;

    public static final int DEFAULT_WORKER_NUMBERS = 5;

    public static final int MIN_WORKER_NUMBERS = 1;

    private AtomicLong threadNum = new AtomicLong();

    private int workNum = DEFAULT_WORKER_NUMBERS;

    private final LinkedList<Job> jobs = new LinkedList<>();

    private final List<Worker> workers = Collections.synchronizedList(new ArrayList<Worker>());


    private void initWorkers(int num){
        for(int i = 0;i < num;i++){
            Worker worker = new Worker();
            workers.add(worker);
            Thread thread = new Thread(worker,"Thread-" + threadNum.incrementAndGet());
            thread.start();
        }
    }

    public DefaultThreadPool(int num){
        initWorkers(num);
    }

    @Override
    public void execute(Job job) {
        if(job!=null){
            synchronized (jobs){
                jobs.addLast(job);
                jobs.notifyAll();
            }
        }
    }

    @Override
    public void shutdown() {
        for (Worker worker:workers){
            worker.shutdown();
        }
    }

    @Override
    public void addWorker(int num) {
        synchronized (jobs){
            if(num+this.workNum > MAX_WORKER_NUMBERS){
                num = MAX_WORKER_NUMBERS-workNum;
            }
            initWorkers(num);
            this.workNum += num;
        }
    }

    @Override
    public void removeWorker(int num) {
        synchronized (jobs){
            if(num > workNum){
                throw new IllegalArgumentException("beyond worknum");
            }
            int count = 0;
            while(count < num){
                Worker worker = workers.get(count);
                if(workers.remove(worker)){
                    worker.shutdown();
                    count++;
                }
            }
            this.workNum -= count;
        }
    }

    @Override
    public int getJobSize() {
        return jobs.size();
    }

    class Worker implements Runnable{
        private volatile boolean running = true;

        @Override
        public void run() {
            while (running){
                Job job = null;
                synchronized (jobs){
                    while(jobs.isEmpty()){
                        try {
                            jobs.wait();
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                    job = jobs.removeFirst();
                }
                if(job != null){
                    job.run();
                }

            }
        }
        public void shutdown(){
            running = false;
        }

    }
}