java - 关于阻塞队列和多线程消费者的一些困惑

Question

我正在编写一些像这样的多线程代码(由于相关性省略了很多细节):

public class Producer {

    private static BlockingQueue<Transaction> transactionsQueue = new LinkedBlockingQueue<Transaction>();
    private static ArrayList<C> consumersList = new ArrayList<C>();

    public Producer(int a, int b) {
        for (int i = 0; i < a; i++)
            accountsList.add(new Account(i, DEFAULT_BALANCE));

        for (int i = 0; i < b; i++)
            consumersList.add(new Consumer());

        for (Consumer c : consumersList)
            c.start(); //question line of code
    }


    public class Consumer extends Thread{
        @Override
        public void run(){
            while (true) {
                try {
                    Transaction nextTransaction = transactionsQueue.take();

                    if(nextTransaction.equals(FINAL_TRANSACTION))
                        break;

                    Account acc = accountsList.get(nextTransaction.getTo());
                    acc.makeTransaction(nextTransaction);
                    System.out.println(acc);

                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    public static void main(String []args){
        try{
            launch(args[0], NUM_OF_ACCOUNTS, Integer.parseInt(args[1]));
        }catch (Exception e){
            System.out.println("Incorrect args. Starting with default arguments");
            launch(SMALL_FILE, NUM_OF_ACCOUNTS, NUM_OF_THREADS);
        }
    }

    private static void launch(String filename, int numOfAccounts, int numOfConsumers) {
        Producer bank = new Producer(numOfAccounts, numOfConsumers);
        bank.createTransactionsQueue(filename); //start putting into transactionsQueue
        bank.close();
    }
}

我的问题是，当程序在 Producer 的构造函数中执行 for (Consumer c :consumersList) c.start(); 时，消费者线程的 run() 方法立即被调用？如果是这样，当 transactionsQueue 为空时会发生什么 - 因为我开始将 put 放入 transactionsQueue at bank.createTransactionsQueue(filename) ; 这是在调用构造函数(并创建消费者线程)之后。

Answer 1

does the consumer threads's run() method immediately gets called

很快就会被调用。它不是执行的下一行，而是在新线程实际启动时执行。

If so what happens when the transactionsQueue is empty

正在运行的其他线程将被挂起，直到队列中有一个元素。对于放置的每个元素，将唤醒一个线程以将元素从队列中拉出。