Java线程间协作wait、notify和notifyAll详解

public final void wait() throws InterruptedException

Causes the current thread to wait until another thread invokes the notify() method or the notifyAll() method for this object. In other words, this method behaves exactly as if it simply performs the call wait(0).

The current thread must own this object's monitor. The thread releases ownership of this monitor and waits until another thread notifies threads waiting on this object's monitor to wake up either through a call to the notify method or the notifyAll method. The thread then waits until it can re-obtain ownership of the monitor and resumes execution.

As in the one argument version, interrupts and spurious wakeups are possible, and this method should always be used in a loop:

     synchronized (obj) {
         while (<condition does not hold>)
             obj.wait();
         ... // Perform action appropriate to condition
     }

This method should only be called by a thread that is the owner of this object's monitor. See the notify method for a description of the ways in which a thread can become the owner of a monitor.

Throws:
    IllegalMonitorStateException - if the current thread is not the owner of the object's monitor.
    InterruptedException - if any thread interrupted the current thread before or while the current thread was waiting for a notification. The interrupted status of the current thread is cleared when this exception is thrown. 

public final void notify()

Wakes up a single thread that is waiting on this object's monitor. If any threads are waiting on this object, one of them is chosen to be awakened. The choice is arbitrary and occurs at the discretion of the implementation. A thread waits on an object's monitor by calling one of the wait methods.

The awakened thread will not be able to proceed until the current thread relinquishes the lock on this object. The awakened thread will compete in the usual manner with any other threads that might be actively competing to synchronize on this object; for example, the awakened thread enjoys no reliable privilege or disadvantage in being the next thread to lock this object.

This method should only be called by a thread that is the owner of this object's monitor. A thread becomes the owner of the object's monitor in one of three ways:

    By executing a synchronized instance method of that object.
    By executing the body of a synchronized statement that synchronizes on the object.
    For objects of type Class, by executing a synchronized static method of that class. 

Only one thread at a time can own an object's monitor.

Throws:
    IllegalMonitorStateException - if the current thread is not the owner of this object's monitor.

/**
 * 
 */
public class Producer extends Thread {

    private volatile Queue<Integer> queue;
    private int maxSize;

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

    @Override
    public void run() {
        while (true) {
            //wait,notify方法必须在同步代码中运行
            synchronized (queue) {
                //条件一定在循环中判断，以防死锁
                while (queue.size() == maxSize) {
                    try {                             System.out.println(Thread.currentThread().getName() + " wait.");
                        queue.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
                int i = new Random().nextInt();
                System.out.println(Thread.currentThread().getName() + " produce: " + i);
                queue.add(i);
                queue.notifyAll();
            }
        }
    }
}

 /**
 * 
 */
public class Consumer extends Thread {

    private volatile Queue<Integer> queue;
    private int maxSize;

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

    @Override
    public void run() {
        while (true) {
            synchronized (queue) {
                while (queue.isEmpty()) {
                    try {
                        System.out.println(Thread.currentThread().getName() + " wait.");
                        queue.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }

                System.out.println(Thread.currentThread().getName() + " consume: " + queue.remove());
                queue.notifyAll();
            }
        }
    }
}

/**
 * 
 */
public class WaitNotifyMain {

    private volatile static Queue<Integer> queue = new LinkedList<>();

    /**
     * @param args
     */
    public static void main(String[] args) {

        Producer producer = new Producer(queue, 10);
        producer.setName("Producer");//设置线程名称
        Consumer consumer = new Consumer(queue, 10);
        consumer.setName("Consumer");

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

    }

}

// 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 
}