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java - Beberapa keraguan tentang notify()/wait()

PHP中文網(wǎng) 2017-05-17 09:58:07

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class MyObject{
    private Queue<String> queue = new ConcurrentLinkedQueue<String>();
    public synchronized void set(String s){
            while(queue.size() >= 10){
                try {
                    wait();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            queue.add(s);
            notify();
    }
}

class Producer implements Runnable{
    private MyObject myObj;
    
    public Producer(MyObject myObj) {
        this.myObj= myObj;
    }

    @Override
    public void run() {
        // 每條線程執(zhí)行30次set
        for (int i = 0; i < 30; i++) {
            this.myObj.set("obj:" + i);
        }
    }
}

public static void main(String[] args){
    Producer producer = new Producer(new MyObject());
        
    // 生成30條線程
    for (int i = 0; i < 10; i++) {
        Thread thread = new Thread(producer);
        thread.start();
    }
    // 運(yùn)行結(jié)果是只set了30次
}

Ragu saya ialah apabila notify() menerbitkan pemberitahuan, mengapa ia tidak membiarkan kaedah wait() thread lain terus dilaksanakan?

PHP中文網(wǎng)

認(rèn)證高級(jí)PHP講師

membalas semua(1)

習(xí)慣沉默2017-05-17 10:00:07 Tingkat 1

Apabila bilangan baris gilir anda melebihi 10, setiap utas anda akan bermula wait()住了, 不會(huì)走到notify()的啊. 你需要一個(gè)單獨(dú)的線程去監(jiān)控隊(duì)列的大小, 大于10的時(shí)候notify() dahulu, anda boleh menukar sedikit

class MyObject {
    private Queue<String> queue = new ConcurrentLinkedQueue<String>();

    private volatile int limit = 10;

    public synchronized void set(String s) {
      if (queue.size() >= limit) {
        try {
          wait();
        } catch (InterruptedException e) {
          e.printStackTrace();
        }
      }
      queue.add(s);
    }

    public synchronized void delta() {
      if (queue.size() >= limit) {
        limit += 10;
        notify();
      }
    }
}

Kemudian ada benang pemantauan

class Monitor implements Runnable {

    private MyObject myObj;

    public Monitor(MyObject myObj) {
      this.myObj = myObj;
    }

    @Override
    public void run() {
      while (true) {
        myObj.delta();
      }
    }
}