方式 一： Synchronized方式
注：此种方式会造成资源的浪费：
利用锁的notifyAll()方法会将所有的线程都唤醒，会造成资源的浪费

class Resource {private String name;private int count = 1;private boolean flag = false;public synchronized void set(String name) {/*对于多个生产者和消费者，为什么要用while来判断标记？原因: 让要被唤醒的线程再判断一次标记，因为现在的标记可能已经不是它原来等待时的状态了*/while (flag) { try {this.wait();} catch (Exception e) {}}this.name = name + "--" + count++;System.out.println(Thread.currentThread().getName() + "...Producer..." + this.name);this.flag = true;/*为什么要用notifyAll()因为需要唤醒对方的线程，如果只用notify()的方式有可能出现只唤醒本方线程的情况导致程序中的所有线程都处于等待的状态下！！！*/this.notifyAll();}public synchronized void out() {while (!flag) {try {this.wait();} catch (Exception e) {}}System.out.println(Thread.currentThread().getName() + ".....Consumer....." + this.name);this.flag = false;this.notifyAll();}
}class Producer implements Runnable {private Resource r;public Producer(Resource r) {this.r = r;}public void run() {while (true) {r.set("+Items+");}}
}class Consumer implements Runnable {private Resource r;public Consumer(Resource r) {this.r = r;}public void run() {while (true) {r.out();}}
}public class ProducerAndConsumer {public static void main(String[] args) {Resource r = new Resource();new Thread(new Producer(r)).start();new Thread(new Producer(r)).start();new Thread(new Consumer(r)).start();new Thread(new Consumer(r)).start();}
}

方式二：
利用Lock的方式显示的声明锁
这种方式可以人唤醒想要唤醒的线程，能够减少资源的浪费

/*JDK1.5中提供了多线程中锁的升级解决方案：将同步中的Synchronized替换成显式的lock操作一个锁可以对应多个Condition对象将object中的wait()、notify()、notifyAll()等方法替换成了Condition对象拥有的方法Condition对象通过lock锁的newCondition()方法来获取。不同类型的线程用不同的Condition对象来实现线程状态的切换，以达到对不同类型的线程进行不同的操作的目的例如：下面的示例中用condition对象来对生产者的线程进行操作，用conditionPro对象来对消费者的线程进行操作，这样就可以实现生产者的线程只唤醒消费者，消费者的线程只唤醒生产者，减少资源的浪费。即两种类型的线程用的同一把锁，但是用的不同的Condition对象，这样就可以实现本方只唤醒对方的线程的操作。*/
import java.util.concurrent.locks.*;class Resource {private String name;private int count = 1;private boolean flag = false;private Lock lock = new ReentrantLock();private Condition condition = lock.newCondition();private Condition conditionPro = lock.newCondition();public void set(String name) throws InterruptedException {lock.lock();try {while (flag)condition.await();this.name = name + "--" + count++;System.out.println(Thread.currentThread().getName() + "...Producer..." + this.name);this.flag = true;conditionPro.signal();} finally {lock.unlock();    // 释放锁的动作一定要执行，否则会造成抛异常之后不释放锁，别的线程拿不到锁}}public void out() throws InterruptedException {lock.lock();try {while (!flag)conditionPro.await();System.out.println(Thread.currentThread().getName() + ".....Consumer....." + this.name);this.flag = false;condition.signal();} finally {lock.unlock();}}
}class Producer implements Runnable {private Resource r;public Producer(Resource r) {this.r = r;}public void run() {while (true) {try {r.set("+Items+");} catch (InterruptedException e) {}}}
}class Consumer implements Runnable {private Resource r;public Consumer(Resource r) {this.r = r;}public void run() {while (true) {try {r.out();} catch (InterruptedException e) {}}}
}public class ProducerAndConsumer {public static void main(String[] args) {Resource r = new Resource();new Thread(new Producer(r)).start();new Thread(new Producer(r)).start();new Thread(new Consumer(r)).start();new Thread(new Consumer(r)).start();}
}