【多线程】自定义线程池 仅供学习

一、阻塞队列

package com.learning.threadpool.customer;

import lombok.extern.slf4j.Slf4j;

import java.util.ArrayDeque;
import java.util.Deque;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;

/**
 * @Author wangyouhui
 * @Description 阻塞队列
 **/
@Slf4j
public class BlockingQueue<T> {
    // 1.任务队列
    private Deque<T> queue = new ArrayDeque<>();
    // 2.锁
    private ReentrantLock lock = new ReentrantLock();
    // 3.生产者条件变量
    private Condition fullWaitSet = lock.newCondition();
    // 4.消费者条件变量
    private Condition emptyWaitSet = lock.newCondition();
    // 5.容量
    private int capcity;

    public BlockingQueue(int capcity){
        this.capcity = capcity;
    }

    // 带超时的阻塞获取
    public T poll(long timeout, TimeUnit timeUnit){
        lock.lock();
        try{
            // 将timeout统一转换为
            long nacos = timeUnit.toNanos(timeout);
            while(queue.isEmpty()){
                try{
                    // 返回的是剩余的时间
                    if(nacos <= 0){
                        return null;
                    }
                    nacos = emptyWaitSet.awaitNanos(nacos);
                }catch (InterruptedException e){
                    e.printStackTrace();
                }
            }
            T t = queue.removeFirst();
            fullWaitSet.signal();
            return t;
        }finally {
            lock.unlock();
        }
    }
    // 阻塞获取
    public T take(){
        lock.lock();
        try{
            while(queue.isEmpty()){
                try {
                    emptyWaitSet.await();
                }catch(InterruptedException e){
                    e.printStackTrace();
                }
            }
            T t = queue.removeFirst();
            fullWaitSet.signal();
            return t;
        }finally {
            lock.unlock();
        }
    }
    // 阻塞添加
    public void put(T task){
        lock.lock();
        try{
            while(queue.size() == capcity){
                try {
                    log.debug("等待加入任务队列 {}", task);
                    fullWaitSet.await();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            queue.addLast(task);
            log.debug("加入任务队列 {}", task);
            emptyWaitSet.signal();
        }finally {
            lock.unlock();
        }
    }

    // 带超时时间阻塞添加
    public boolean offer(T task, long timeout, TimeUnit timeUnit){
        lock.lock();
        try{
            long nacos = timeUnit.toNanos(timeout);
            while(queue.size() == capcity){
                try {
                    log.debug("等待加入任务队列 {}", task);
                    if(nacos <= 0){
                        return false;
                    }
                    nacos = fullWaitSet.awaitNanos(nacos);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            queue.addLast(task);
            log.debug("加入任务队列 {}", task);
            emptyWaitSet.signal();
            return true;
        }finally {
            lock.unlock();
        }
    }

    // 获取大小
    public int size(){
        lock.lock();
        try{
            return queue.size();
        }finally {
            lock.unlock();
        }
    }

    public void tryPut(RejectPolicy<T> rejectPolicy, T task) {
        lock.lock();
        try{
            // 判断队列是否已满
            if(queue.size() == capcity){
                rejectPolicy.reject(this, task);
            }else{
                // 有空闲
                log.debug("加入任务队列{}", task);
                queue.add(task);
                emptyWaitSet.signal();
            }
        }finally {
            lock.unlock();
        }
    }
}

二、拒绝策略接口

package com.learning.threadpool.customer;

/**
 * 拒绝策略
 */
@FunctionalInterface
public interface RejectPolicy<T> {
    void reject(BlockingQueue<T> tBlockingQueue, T task);
}

三、自定义线程池

package com.learning.threadpool.customer;

import lombok.extern.slf4j.Slf4j;

import java.util.HashSet;
import java.util.concurrent.TimeUnit;

/**
 * @Date 2023/7/10 14:37
 * @Description 自定义线程池
 */
@Slf4j
public class ThreadPool {
    // 任务队列
    private BlockingQueue<Runnable> taskQueue;

    // 线程集合
    private HashSet<Worker> workers = new HashSet();

    // 核心线程数
    private int coreSize;

    // 超时时间
    private long timeout;

    // 超时时间单位
    private TimeUnit timeUnit;

    private RejectPolicy<Runnable> rejectPolicy;

    public ThreadPool(int coreSize, long timeout, TimeUnit timeUnit, int queueCapcity, RejectPolicy<Runnable> rejectPolicy){
        this.coreSize = coreSize;
        this.timeout = timeout;
        this.timeUnit = timeUnit;
        this.taskQueue = new BlockingQueue<>(queueCapcity);
        this.rejectPolicy = rejectPolicy;
    }

    // 执行任务
    public void execute(Runnable task){
        // 当任务数没有超过核心线程数时，直接交给worker对象执行
        synchronized (this) {
            if (workers.size() < coreSize) {
                Worker worker = new Worker(task);
                log.debug("新增worker {} 任务对象 {}", worker, task);
                workers.add(worker);
                worker.start();
            } else {
                // 如果任务数超过了核心线程数，加入任务队列暂存
//                taskQueue.put(task);
                // 当队列满了，可以死等、带超时等待、放弃任务执行、抛出异常、让调用者自己调用任务
                taskQueue.tryPut(rejectPolicy, task);
            }
        }
    }

    class Worker extends Thread{
        private Runnable task;

        private Worker(Runnable task){
            this.task = task;
        }

        @Override
        public void run(){
            // 执行任务
            // 1.当task不为空，执行任务
            // 2.当task执行完毕，再从任务队列中获取任务并执行
//            while(task != null || (task = taskQueue.take()) != null){
            while(task != null || (task = taskQueue.poll(timeout, timeUnit)) != null){
                try{
                    log.debug("正在运行...{}", task);
                    task.run();
                }catch (Exception e){
                    e.printStackTrace();
                }finally {
                    task = null;
                }
            }
            synchronized (workers){
                log.debug("worker 被移除 {}", this);
                workers.remove(this);
            }
        }
    }
}

四、测试类

package com.learning.threadpool.customer;

import lombok.extern.slf4j.Slf4j;

import java.util.concurrent.TimeUnit;

/**
 * @Date 2023/7/10 15:32
 * @Description 启动类
 */
@Slf4j
public class Application {
    public static void main(String[] args) {
        ThreadPool threadPool = new ThreadPool(1, 1000, TimeUnit.MILLISECONDS, 1, (queue, task)->{
            // 1.死等
//            queue.put(task);
//            // 2.带超时等待
//            queue.offer(task, 1500, TimeUnit.MILLISECONDS);
            // 3.让调用者放弃任务执行
            log.debug("放弃 {}", task);
            // 4.让调用者抛出异常
//            throw new RuntimeException("任务执行失败" + task);
            // 5.让调用者自己执行任务
            task.run();
        });
        for (int i = 0; i < 3; i++) {
            int j = i;
            threadPool.execute(()->{
                try {
                    Thread.sleep(1000L);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                log.debug("{}", j);
            });
        }
    }
}