Concepts of Programming Languages

13.7 Java Threads 611

int new_item;
while (true) {
//-- Create a new_item
buffer.deposit(new_item);
}
}
}

class Consumer extends Thread {
private Queue buffer;
public Consumer(Queue que) {
buffer = que;
}
public void run() {
int stored_item;
while (true) {
stored_item = buffer.fetch();
//-- Consume the stored_item
}
}
}

The following code creates a Queue object, and a Producer and a Con-
sumer object, both attached to the Queue object, and starts their execution:

Queue buff1 = new Queue(100);
Producer producer1 = new Producer(buff1);
Consumer consumer1 = new Consumer(buff1);
producer1.start();
consumer1.start();

We could define one or both of the Producer and the Consumer as imple-
mentations of the Runnable interface rather than as subclasses of Thread.
The only difference is in the first line, which would now appear as

class Producer implements Runnable {... }

To create and run an object of such a class, it is still necessary to create a
Thread object that is connected to the object. This is illustrated in the fol-
lowing code:

Producer producer1 = new Producer(buff1);
Thread producerThread = new Thread(producer1);
producerThread.start();

Note that the buffer object is passed to the Producer constructor and the
Producers object is passed to the Thread constructor.