自定义线程池

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;

/**
 * 自定义线程池
 */
@Slf4j
public class Test17 {
    public static void main(String[] args) {
        ThreadPool threadPool = new ThreadPool(2, 1000, TimeUnit.MILLISECONDS, 10,((queue, task) -> {
            //1）死等
//            queue.put(task);
            //2）带超时等待
//            queue.offer(task, 5, TimeUnit.SECONDS);
            //5) 让调用者放弃任务执行

            //3) 抛出异常
//            throw new RuntimeException("");
            //4) 让调用者自己执行任务
            task.run();

        }));
        for (int i = 0; i < 5; i++) {
            int j = i;
            threadPool.execute(()->{
                log.info("{}",j);
            });
        }
    }
}

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

@Slf4j
class ThreadPool {
    //任务队列
    private BlockQueue<Runnable> taskQueue;
    //线程集合
    private HashSet<Worker> workers = new HashSet();
    //核心线程数
    private int coreSize;
    //获取任务的超时时间
    private long timeout;
    //时间单位
    private TimeUnit timeUnit;

    private RejectPolicy<Runnable> rejectPolicy;


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

    //执行任务
    public void execute(Runnable task) {
           //当任务数没有超过coreSize时，直接交给worker对象执行
            //如果任务数超过coreSize时，加入任务队列暂存
        synchronized (workers) {
            if (workers.size() < coreSize) {
                Worker worker = new Worker(task);
                log.info("新增 worker {},{}",worker,task);
                workers.add(worker);
                worker.start();
            } else {
                //1）死等
                //2）带超时等待
                //5) 让调用者放弃任务执行
                //3) 抛出异常
                //4) 让调用者自己执行任务
                taskQueue.tryPut(rejectPolicy, task);
            }
        }
    }

    class Worker extends Thread{
        private Runnable task;
        public 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，再接着从任务队列中获取任务并执行
            while (task != null || (task = taskQueue.poll(timeout,timeUnit))!=null) {
                try {
                    task.run();
                } catch (Exception e) {
                    e.printStackTrace();
                }finally {
                    task =null;
                }
            }
            synchronized (workers) {
                workers.remove(this);
            }
        }
    }

}

@Slf4j
class BlockQueue<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 capacity;

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

    //带超时的阻塞获取
    public T poll(long timeout, TimeUnit unit) {
        lock.lock();
        try {
            //将timeout统一转换为纳秒
            long nanos = unit.toNanos(timeout);
            while (queue.isEmpty()) {
                try {
                    if (nanos<=0) {
                        return null;
                    }
                    //返回的是剩余时间
                    nanos = emptyWaitSet.awaitNanos(nanos);
                } 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 element) {
        lock.lock();
        try {
            while (queue.size() == capacity) {
                try {
                    fullWaitSet.await();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            queue.addLast(element);
            emptyWaitSet.signal();
        }finally {
            lock.unlock();
        }

    }

    //带超时事件的阻塞添加
    public boolean offer(T task,long timeout,TimeUnit unit) {
        lock.lock();
        try {
            long nanos = unit.toNanos(timeout);
            while (queue.size() == capacity) {
                if (nanos<=0) {
                    return false;
                }
                try {
                    nanos = fullWaitSet.awaitNanos(nanos);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            queue.addLast(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() == capacity) {
                rejectPolicy.reject(this,task);
            }else {
                queue.addLast(task);
                emptyWaitSet.signal();
            }
        }finally {
            lock.unlock();
        }
    }
}