我在学习多线程的生产者-消费者模式。其基本思想是一个生产者线程将数据放入阻塞队列，然后许多消费者线程将从队列中获取数据。
使用者的“run（）”方法如下所示。

@Override
    public void run() {
        List<String> record;
        while(true) {
            if(this.channel.getState()) {
                break;
            }
            try {
//                System.out.println(this.channel.getSharedQueue().size());
                record = this.channel.getSharedQueue().take();
                ...
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        record = null;
    }

当我注解掉“system.out.println（…）”时，整个程序都会卡住。但是，如果添加“system.out.println（…）”，程序将平稳运行。有人能解释一下“system.out.println（…）”背后的魔力吗？
下面是生产者的“run（）”方法。

public void run() {
        ...
            while ((line = br.readLine()) != null && line.length() > 1) {
                List<String> record = parseRow(line);
                if(record != null)
                    this.channel.getSharedQueue().put(record);
            }
        ...
        this.channel.setState(true);
    }

以及主要的方法。

ExecutorService producerExecutor = Executors.newSingleThreadExecutor();
        Runnable producer = new Producer(channel, ...);
        producerExecutor.execute(producer);

        ExecutorService consumerExecutor = Executors.newFixedThreadPool(30);
        for(int i = 0; i < 30; i++) {
            Runnable consumer = new Consumer(channel);
            consumerExecutor.execute(consumer);
        }

        consumerExecutor.shutdown();
        producerExecutor.shutdown();
        while (!consumerExecutor.isTerminated() || !producerExecutor.isTerminated());

channel类就像

public class Channel {

    private volatile boolean state;

    ...

    public boolean getState() {
        return this.state;
    }

    public void setState(boolean state) {
        this.state = state;
    }

    ...
}

谢谢你的帮助！