生产者-消费者与队列的简单示例

/** *生产者-消费者与队列 *制作吐司的例子，先向干吐司抹黄油，再在抹过黄油的吐司上涂果酱 *本例子没有使用任何显式的同步，而是利用阻塞队列来实现同步 *每片吐司在任何时刻都只由一个任务在操作 * * @author c * @data 2016-08-31 * @modify * */ class Toast { public enum Status { DRY, BUTTERED, JAMMED } private Status status = Status.DRY; private final int id; public Toast(int idn) { id = idn; } public void buffer() { status = Status.BUTTERED; } public void jam() { status = Status.JAMMED; } public Status getStatus() { return status; } public int getId() { return id; } public String toString() { return "Toast " + id + ": " + status; } } class ToastQueue extends LinkedBlockingQueue<Toast> { } class Toaster implements Runnable { private ToastQueue toastQueue; private int count = 0; private Random rand = new Random(47); public Toaster(ToastQueue tq) { toastQueue = tq; } public void run() { try { while (!Thread.interrupted()) { TimeUnit.MILLISECONDS.sleep(100 + rand.nextInt(500)); // 制作吐司 Toast t = new Toast(count++); print(t); // 插入队列 toastQueue.put(t); } } catch (InterruptedException e) { print("Toaster interrupted"); } print("Toaster off"); } } // 给吐司抹黄油 class Butterer implements Runnable { private ToastQueue dryQueue, butteredQueue; public Butterer(ToastQueue dry, ToastQueue buttered) { dryQueue = dry; butteredQueue = buttered; } @Override public void run() { try { while (!Thread.interrupted()) { // 阻塞直到下一份可利用的吐司 Toast t = dryQueue.take(); t.buffer(); print(t); butteredQueue.put(t); } } catch (InterruptedException e) { print("Butterer interrupted"); } print("Butterer off"); } } // 在抹过黄油的吐司上涂果酱 class Jammer implements Runnable { private ToastQueue butteredQueue, finishedQueue; public Jammer(ToastQueue buttered, ToastQueue finished) { butteredQueue = buttered; finishedQueue = finished; } @Override public void run() { try { while (!Thread.interrupted()) { // 阻塞直到下一份吐司可以利用 Toast t = butteredQueue.take(); t.jam(); print(t); finishedQueue.put(t); } } catch (InterruptedException e) { print("Jammer interrupted"); } print("Jammer off"); } } // 消费吐司 class Eater implements Runnable { private ToastQueue finishedQueue; private int counter = 0; public Eater(ToastQueue finished) { finishedQueue = finished; } @Override public void run() { try { while (!Thread.interrupted()) { // 阻塞直到下一份吐司可以利用 Toast t = finishedQueue.take(); // 确认吐司按顺序到来和所有吐司都抹了果酱 if (t.getId() != counter++ || t.getStatus() != Toast.Status.JAMMED) { print(">>>> Error " + t); System.exit(1); } else print("chomp!" + t); } } catch (InterruptedException e) { print("Eater interrupted"); } print("Eater off"); } } public class ToastOMatic { public static void main(String[] args) throws Exception { ToastQueue dryQueue = new ToastQueue(), butteredQueue = new ToastQueue(), finishedQueue = new ToastQueue(); ExecutorService exec = Executors.newCachedThreadPool(); exec.execute(new Toaster(dryQueue)); exec.execute(new Butterer(dryQueue, butteredQueue)); exec.execute(new Jammer(butteredQueue, finishedQueue)); exec.execute(new Eater(finishedQueue)); TimeUnit.SECONDS.sleep(5); exec.shutdownNow(); } }