一个关于Java Thread wait(),notify()的实用例【转】
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package cn.com.dang; public class ProducerConsumer { public static void main(String[] args) { ProductStack ps = new ProductStack(); Producer p = new Producer(ps, "生产者1"); Consumer c = new Consumer(ps, "消费者1"); new Thread(p).start(); new Thread(c).start(); }} class Product { int id; private String producedBy = "N/A"; private String consumedBy = "N/A"; // 构造函数，指明产品ID以及生产者名字。 Product(int id, String producedBy) { this.id = id; this.producedBy = producedBy; } // 消费，需要指明消费者名字 public void consume(String consumedBy) { this.consumedBy = consumedBy; } public String toString() { return "Product : " + id + ", produced by " + producedBy + ", consumed by " + consumedBy; } public String getProducedBy() { return producedBy; } public void setProducedBy(String producedBy) { this.producedBy = producedBy; } public String getConsumedBy() { return consumedBy; } public void setConsumedBy(String consumedBy) { this.consumedBy = consumedBy; } } // 这个class就是仓库，是生产者跟消费者共同争夺控制权的同步资源class ProductStack { int index = 0; Product[] arrProduct = new Product[6]; // push使用来让生产者放置产品的 public synchronized void push(Product product) { // 如果仓库满了 while (index == arrProduct.length) // 这里本来可以用if(),但是如果catch // exception会出问题，让满的index越界 { try { // here, "this" means the thread that is using "push" // so in this case it's a producer thread instance. // the BIG difference between sleep() and wait() is, once // wait(), // the thread won't have the lock anymore // so when a producer wait() here, it will lost the lock of // "push()" // While sleep() is still keeping this lock // Important: wait() and notify() should be in "synchronized" // block System.out.println(product.getProducedBy() + " is waiting."); // 等待，并且从这里退出push() wait(); } catch (InterruptedException e) { e.printStackTrace(); } } System.out.println(product.getProducedBy() + " sent a notifyAll()."); // 因为我们不确定有没有线程在wait()，所以我们既然生产了产品，就唤醒有可能等待的消费者，让他们醒来，准备消费 notifyAll(); // 注意，notifyAll()以后，并没有退出，而是继续执行直到完成。 arrProduct[index] = product; index++; System.out.println(product.getProducedBy() + " 生产了: " + product); } // pop用来让消费者取出产品的 public synchronized Product pop(String consumerName) { // 如果仓库空了 while (index == 0) { try { // here will be the consumer thread instance will be waiting , // because empty System.out.println(consumerName + " is waiting."); // 等待，并且从这里退出pop() wait(); } catch (InterruptedException e) { e.printStackTrace(); } } System.out.println(consumerName + " sent a notifyAll()."); // 因为我们不确定有没有线程在wait()，所以我们既然消费了产品，就唤醒有可能等待的生产者，让他们醒来，准备生产 notifyAll(); // 注意，notifyAll()以后，并没有退出，而是继续执行直到完成。 // 取出产品 index--; Product product = arrProduct[index]; product.consume(consumerName); System.out.println(product.getConsumedBy() + " 消费了: " + product); return product; }} class Producer implements Runnable { String name; ProductStack ps = null; Producer(ProductStack ps, String name) { this.ps = ps; this.name = name; } public void run() { for (int i = 0; i < 20; i++) { Product product = new Product(i, name); ps.push(product); try { Thread.sleep((int) (Math.random() * 200)); } catch (InterruptedException e) { e.printStackTrace(); } } }} class Consumer implements Runnable { String name; ProductStack ps = null; Consumer(ProductStack ps, String name) { this.ps = ps; this.name = name; } public void run() { for (int i = 0; i < 20; i++) { Product product = ps.pop(name); try { Thread.sleep((int) (Math.random() * 1000)); } catch (InterruptedException e) { e.printStackTrace(); } } }}?