生产者-消费者

产者消费者问题是多线程的一个经典问题，它描述是有一块缓冲区作为仓库，生产者可以将产品放入仓库，消费者则可以从仓库中取走产品。

wait()方法：当缓冲区已满/空时，生产者/消费者线程停止自己的执行，放弃锁，使自己处于等等状态，让其他线程执行。
notify()方法：当生产者/消费者向缓冲区放入/取出一个产品时，向其他等待的线程发出可执行的通知，同时放弃锁，使自己处于等待状态。

缓冲区

public class Storage {
    // 仓库最大存储量
    private final int MAX_SIZE = 100;

    // 仓库存储的载体
    private LinkedList<Object> list = new LinkedList<Object>();

    public int getMAX_SIZE() {
        return MAX_SIZE;
    }

    public LinkedList<Object> getList() {
        return list;
    }

    public void setList(LinkedList<Object> list) {
        this.list = list;
    }

    // 生产产品
    public void produce(String producer){
        synchronized (list){
            while (list.size() == MAX_SIZE){
                System.out.println("仓库已满，【"+producer+"】： 暂时不能执行生产任务!");
                try{
                    list.wait();
                }catch (Exception e){
                    e.printStackTrace();
                }
            }

            list.add(new Object());

            System.out.println("【"+producer+"】：生产了一个产品\t【现仓储量为】:" + list.size());

            list.notifyAll();
        }
    }

    // 消费产品
    public void consume(String consumer) {
        synchronized (list) {
            //如果仓库存储量不足
            while (list.size()==0) {
                System.out.println("仓库已空，【"+consumer+"】： 暂时不能执行消费任务!");
                try {
                    // 由于条件不满足，消费阻塞
                    list.wait();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
            list.remove();
            System.out.println("【"+consumer+"】：消费了一个产品\t【现仓储量为】:" + list.size());
            list.notifyAll();
        }
    }

}

生产者：

public class Producer  extends Thread{
    private String producer;
    private Storage storage;

    public String getProducer() {
        return producer;
    }

    public void setProducer(String producer) {
        this.producer = producer;
    }

    public Storage getStorage() {
        return storage;
    }

    public void setStorage(Storage storage) {
        this.storage = storage;
    }

    public Producer(Storage storage,String producer) {
        this.storage = storage;
        this.producer = producer;
    }

    @Override
    public void run() {
        produce(producer);
    }

    public void produce(String producer) {
        storage.produce(producer);
    }
}

消费者：

public class Consumer extends Thread {
    private String consumer;
    private Storage storage;

    public Consumer(Storage storage,String consumer) {
        this.storage = storage;
        this.consumer = consumer;
    }

    @Override
    public void run() {
        consume(consumer);
    }

    public void consume(String consumer) {
        storage.consume(consumer);
    }

    public String getConsumer() {
        return consumer;
    }

    public void setConsumer(String consumer) {
        this.consumer = consumer;
    }

    public Storage getStorage() {
        return storage;
    }

    public void setStorage(Storage storage) {
        this.storage = storage;
    }
}

test：

public class Test {
    public static void main(String[] args) {
        Storage storage = new Storage();
        new Thread(new Consumer(storage,"消费者1")).start();
        new Thread(new Producer(storage,"生产者A")).start();
        new Thread(new Consumer(storage,"消费者2")).start();
        new Thread(new Producer(storage,"生产者B")).start();
        new Thread(new Producer(storage,"生产者C")).start();
        new Thread(new Consumer(storage,"消费者3")).start();
        new Thread(new Consumer(storage,"消费者4")).start();

    }
}

截图：