如何使用wait

在synchronized的函数或对象里使用wait、notify和notifyAll，不然Java虚拟机会生成 IllegalMonitorStateException
永远在多线程间共享的对象上使用wait，也就是在synchronized的对象上。

永远在循环里调用 wait 和 notify，不是在 If 中

// The standard idiom for calling the wait method in Java
synchronized (sharedObject) {
while (condition) {
sharedObject.wait();
// (Releases lock, and reacquires on wakeup)
}
// do action based upon condition e.g. take or put into queue
}

生产者消费者示例

/**
 * 生产者消费者示例
 * <p>生成N个 消费N个</p>
 */
public class ProducerConsumerTest {

    class Producer extends Thread {
        private Queue<Integer> queue;
        private int            maxSize;

        Producer(Queue<Integer> queue, int maxSize) {
            this.queue = queue;
            this.maxSize = maxSize;
        }

        @Override
        public void run() {

            synchronized (queue) {
                //while 一定要放在同步代码内部
                while (true) {
                    //如果要交替打印,可将条件改为： !queue.isEmpty()
                    while (queue.size() == maxSize) {
                        try {
                            queue.wait();
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                    System.out.println("生产1个");
                    queue.add(1);
                    //如果多个消费者 可改为notifyAll
                    queue.notify();
                }
            }
        }
    }

    class Consumer extends Thread {
        private Queue<Integer> queue;

        Consumer(Queue<Integer> queue) {
            this.queue = queue;
        }

        @Override
        public void run() {

            synchronized (queue) {
                while (true) {
                    while (queue.isEmpty()) {
                        try {
                            queue.wait();
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                    System.out.println("消费1个");
                    queue.remove();
                    queue.notify();
                }
            }
        }
    }

    public static void main(String[] args) {
        Queue<Integer> queue = new LinkedList<>();
        ProducerConsumerTest test = new ProducerConsumerTest();

        Producer producer = test.new Producer(queue, 10);
        Consumer consumer = test.new Consumer(queue);

        producer.start();
        consumer.start();
    }
}

效果如下：