java多線程之wait和notify

1. 使用注意事項

1、永遠在synchronized的函數或對象裏使用wait、notify和notifyAll，不然Java虛擬機會生成IllegalMonitorStateException。
2、永遠在while循環裏而不是if語句下使用wait。這樣，循環會在線程睡眠前後都檢查wait的條件，並在條件實際上並未改變的情況下處理喚醒通知。
3、永遠在多線程間共享的對象上使用wait。
4、notify隨機通知一個阻塞在對象上的線程；notifyAll通知阻塞在對象上所有的線程。

2. 代碼示例

2.1 生產者

public class Producer implements Runnable{

    private 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){
            synchronized (queue){
                while (queue.size() == maxSize){
                    try{
                        System.out.println("Queue is Full");
                        queue.wait();
                    }catch (InterruptedException ie){
                        ie.printStackTrace();
                    }
                }
                Random random = new Random();
                int i = random.nextInt();
                System.out.println("Produce " + i);
                queue.add(i);
                queue.notifyAll();
            }
        }
    }
}

2.2 消費者

public class Consumer implements Runnable{

    private 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()){
                    System.out.println("Queue is Empty");
                    try{
                        queue.wait();
                    }catch (InterruptedException ie){
                        ie.printStackTrace();
                    }
                }
                int v = queue.remove();
                System.out.println("Consume " + v);
                queue.notifyAll();
            }
        }
    }
}

2.3 Main

public class Main {
    public static void main(String[] args){
        Queue<Integer> queue = new LinkedList<>();
        int maxSize = 10;
        Producer p = new Producer(queue, maxSize);
        Consumer c = new Consumer(queue, maxSize);
        Thread pT = new Thread(p);
        Thread pC = new Thread(c);
        pT.start();
        pC.start();
    }
}

3. 參考

https://www.cnblogs.com/plmnko/archive/2010/10/15/1851854.html