手写简易线程池
/**手写简易的线程池 * @author 胡庆安 * @version V1.0 * @Package Thread.pool * @date 2020/10/23 10:57 * @Copyright © 2010-2020 爬山虎科技（扬州）股份有限公司 */ public class HqaPool { /** * 核心线程数 */ int coreSize; /** * 队列存放最大任务数 */ int capcity; /** * 闲置多久线程会被会被回收 */ long times; HashSet<Task> tasks = new HashSet<>(); BlockingQueue queue; public HqaPool(int coreSize, int capcity, long times) { this.coreSize = coreSize; this.capcity = capcity; this.times = times; queue = new BlockingQueue(capcity); } //执行任务 public void execute(Runnable task){ synchronized (tasks){ Task taskRe = new Task(task); //如果任务没有超过coreSize,直接交给Task对象执行 if(tasks.size()<coreSize){ tasks.add(taskRe); taskRe.start(); }else {//如果任务超过了coreSize,直接添加到队列等待 queue.put(taskRe); System.out.println("任务"+taskRe+"被添加到了队列里"); } } } /** * 阻塞任务队列（存放任务） */ class BlockingQueue{ private Deque<Task> deque = new ArrayDeque<Task>(); public ReentrantLock lock = new ReentrantLock(); private int capcity; //生产者条件变量 private Condition fullWaitSet = lock.newCondition(); //消费者条件变量 private Condition emptyWaitSet = lock.newCondition(); public BlockingQueue(int capcity) { this.capcity = capcity; } //任务放入阻塞队列 public void put(Task task){ lock.lock(); try { while (deque.size() == capcity){ try { fullWaitSet.await(); } catch (InterruptedException e) { e.printStackTrace(); } } deque.add(task); emptyWaitSet.signal(); }finally { lock.unlock(); } } //任务取出阻塞队列 public Task take(){ Task task; lock.lock(); try { while (deque.size() == 0){ try { emptyWaitSet.await(); } catch (InterruptedException e) { e.printStackTrace(); } } task= deque.removeFirst(); fullWaitSet.signal(); }finally { lock.unlock(); } return task; } //获取阻塞队列当前的size public int size(){ lock.lock(); try { return deque.size(); }finally { lock.lock(); } } } /** * 线程池任务 */ class Task extends Thread{ private Runnable task; public Task(Runnable task) { this.task = task; } @Override public void run() { while (task!=null||(task=queue.take()) != null){//请细品 try { System.out.println("任务"+task+"被执行了"); task.run(); }catch (Exception e){ e.printStackTrace(); }finally { task = null; } } } } }
测试main方法：
public static void main(String[] args) { HqaPool pool = new HqaPool(2, 10, 1000); for (int i = 0; i < 15; i++) { pool.execute(() -> { try { Thread.sleep(5000L); } catch (InterruptedException e) { e.printStackTrace(); } }); } }
注意上面的程序当线程逻辑执行完之后程序不会结束，会一直阻塞在task=queue.take()那里，所以我们手写线程池2.0 的版本会给阻塞队列添加超时获取的功能以及拒绝策略等功能。。。。。。。
下面是2.0 版本：
/** * @author 胡庆安 * @version V2.0 * @Package Thread.pool * @date 2020/10/23 14:01 * @Copyright © 2010-2020 爬山虎科技（扬州）股份有限公司 */ public class ThreadPool { Logger log = LoggerFactory.getLogger(ThreadPool.class); // 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; // 获取任务时的超时时间 private long timeout; private TimeUnit timeUnit; // 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.debug("新增 worker{}, {}", worker, task); workers.add(worker); worker.start(); } else { // taskQueue.put(task); // 1) 死等 // 2) 带超时等待 // 3) 让调用者放弃任务执行 // 4) 让调用者抛出异常 // 5) 让调用者自己执行任务 taskQueue.offer(task,1000,TimeUnit.SECONDS); } } } public ThreadPool(int coreSize, long timeout, TimeUnit timeUnit, int queueCapcity) { this.coreSize = coreSize; this.timeout = timeout; this.timeUnit = timeUnit; this.taskQueue = new BlockingQueue<>(queueCapcity); } 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("正在执行...{}", task); task.run(); } catch (Exception e) { e.printStackTrace(); } finally { task = null; } } synchronized (workers) { log.debug("worker 被移除{}", this); workers.remove(this); } } } 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 { // 返回值是剩余时间 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(); } } // 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(); } } log.debug("加入任务队列 {}", task); queue.addLast(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 nanos = timeUnit.toNanos(timeout); while (queue.size() == capcity) { try { if (nanos <= 0) { return false; } log.debug("等待加入任务队列 {} ...", task); nanos = fullWaitSet.awaitNanos(nanos); } catch (InterruptedException e) { e.printStackTrace(); } } log.debug("加入任务队列 {}", task); queue.addLast(task); emptyWaitSet.signal(); return true; } finally { lock.unlock(); } } public int size() { lock.lock(); try { return queue.size(); } finally { lock.unlock(); } } } }
