自定义线程池简单实现

自定义线程池简单实现

1. 自定义线程池参数有核心线程数、任务超时时间、线程集合、任务队列、拒绝策略。

package org.dsg.jdk.locks;

import lombok.extern.slf4j.Slf4j;

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

@Slf4j(topic = "c.diyThreadPool")
public class DiyThreadPool {

    //任务队列
    private BlockingQueue<Runnable> taskQueue;
    //线程集合
    private final HashSet<Worker> workers = new HashSet<>();
    //核心线程数
    private int coolSize;
    //获取任务的超时
    private long timeout;
    private TimeUnit timeUnit;
    private RejectPolicy<Runnable> rejectPolicy;

    public DiyThreadPool(int coolSize, long timeout, TimeUnit timeUnit, int capacity, RejectPolicy<Runnable> rejectPolicy) {
        this.coolSize = coolSize;
        this.timeout = timeout;
        this.timeUnit = timeUnit;
        this.taskQueue = new BlockingQueue<>(capacity);
        this.rejectPolicy = rejectPolicy;
    }

    public void execute(Runnable task){
        //如果任务数没超过核心线程数，直接交给worker对象执行，否则加入任务队列等待
        synchronized(workers) {
            if (workers.size() < coolSize) {
                Worker worker = new Worker(task);
                log.info("添加worker {}, {}", worker, task);
                workers.add(worker);
                worker.start();
            } else {
                taskQueue.tryPut(rejectPolicy, task);
            }
        }
    }

    class Worker extends Thread {
        private Runnable task;

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

        @Override
        public void run() {
            //1.当task不为空，执行任务
            //2.当task执行完毕，接着从任务队列中获取任务执行
            while(task != null || (task = taskQueue.poll(timeout, timeUnit)) != null){
                try {
                    log.info("执行... {}", task);
                    task.run();
                } catch (Exception e) {
                    e.printStackTrace();
                }finally {
                    task = null;
                }
            }

            synchronized(workers){
                log.info("任务移除 {}", this);
                workers.remove(this);
            }
        }
    }

    public static void main(String[] args) {
        DiyThreadPool threadPool = new DiyThreadPool(1, 1000, TimeUnit.MILLISECONDS, 1, (queue, task)->{
            //queue.put(task); 死等
            //queue.offer(task, 1500, TimeUnit.MILLISECONDS); 带超时等待
            //log.info("放弃{}", task); 让调用者放弃任务执行
            //throw new RuntimeException(""); 让调用者跑出异常
            //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(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                log.info("{}", j);
            });
        }
    }
}

@FunctionalInterface
interface RejectPolicy<T> {
    void reject(BlockingQueue<T> queue, T task);
}

@Slf4j(topic = "c.blockingQueue")
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();
    //容量
    private int capacity;

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

    public T poll(long timeout, TimeUnit timeUnit){
        lock.lock();
        try {
            long nanos = timeUnit.toNanos(timeout);
            while(queue.isEmpty()){
                try {
                    //返回的是剩余时间
                    if(nanos <= 0){
                        return null;
                    }

                    nanos = emptyWaitSet.awaitNanos(nanos);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }

            T t = queue.removeFirst();
            fullWaitSet.signal();
            return t;
        } finally {
            lock.unlock();
        }
    }

    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();
        }
    }

    public void put(T data){
        lock.lock();
        try {
            while(queue.size() == capacity){
                try {
                    log.info("等待加入任务队列 {}", data);
                    fullWaitSet.await();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            log.info("放入任务队列 {}", data);
            queue.addLast(data);
            emptyWaitSet.signal();
        } finally {
            lock.unlock();
        }
    }

    public boolean offer(T task, long timeout, TimeUnit timeUnit){
        lock.lock();
        try {
            long nanos = timeUnit.toNanos(timeout);
            while(queue.size() == capacity){
                try {
                    log.info("等待加入任务队列 {}", task);
                    if(nanos <= 0){
                        return false;
                    }
                    nanos = fullWaitSet.awaitNanos(nanos);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            log.info("放入任务队列 {}", task);
            queue.addLast(task);
            emptyWaitSet.signal();
            return true;
        } finally {
            lock.unlock();
        }
    }

    public void tryPut(RejectPolicy<T> rejectPolicy, T task) {
        lock.lock();
        try{
            if(queue.size() == capacity){
                rejectPolicy.reject(this, task);
            }else{
                log.info("加入任务队列 {}", task);
                queue.addLast(task);
                emptyWaitSet.signal();
            }
        }finally {
            lock.unlock();
        }
    }

    public int size(){
        lock.lock();
        try {
            return queue.size();
        } finally {
            lock.unlock();
        }
    }

}