Concurrency - Java: How to Program Early Objects - page 986

Queue object's take method (line 25). This method call blocks if necessary until there's an
element in the buffer to remove. Lines 18-19 and 26-27 use the ArrayBlockingQueue
object's size method to display the total number of elements currently in the Array-
BlockingQueue .

Class BlockingBufferTest
Class BlockingBufferTest (Fig. 23.15) contains the main method that launches the ap-
plication. Line 13 creates an ExecutorService , and line 16 creates a BlockingBuffer ob-
ject and assigns its reference to the Buffer variable sharedLocation . Lines 18-19 execute
the Producer and Consumer Runnable s. Line 21 calls method shutdown to end the appli-
cation when the threads finish executing the Producer and Consumer tasks and line 22
waits for the scheduled tasks to complete.

1 // Fig. 23.15: BlockingBufferTest.java

2 // Two threads manipulating a blocking buffer that properly

3 // implements the producer/consumer relationship.

4 import java.util.concurrent.ExecutorService;

5 import java.util.concurrent.Executors;

6 import java.util.concurrent.TimeUnit;

7
8

public class BlockingBufferTest

9

{

10 public static void main(String[] args) throws InterruptedException

11 {

12 // create new thread pool with two threads

13 ExecutorService executorService = Executors.newCachedThreadPool();

14
15 // create BlockingBuffer to store ints

Buffer sharedLocation = new BlockingBuffer(); 16

17
18 executorService.execute( new Producer(sharedLocation));

executorService.execute( new Consumer(sharedLocation)); 19

20
21 executorService.shutdown();

22 executorService.awaitTermination( 1 , TimeUnit.MINUTES );

23 }

24 } // end class BlockingBufferTest

Producer writes 1 Buffer cells occupied: 1
Consumer reads 1 Buffer cells occupied: 0
Producer writes 2 Buffer cells occupied: 1
Consumer reads 2 Buffer cells occupied: 0
Producer writes 3 Buffer cells occupied: 1
Consumer reads 3 Buffer cells occupied: 0
Producer writes 4 Buffer cells occupied: 1
Consumer reads 4 Buffer cells occupied: 0
Producer writes 5 Buffer cells occupied: 1
Consumer reads 5 Buffer cells occupied: 0
Producer writes 6 Buffer cells occupied: 1

Fig. 23.15 | Two threads manipulating a blocking buffer that properly implements the
producer/consumer relationship. (Part 1 of 2.)