Concurrency - Java: How to Program Early Objects - page 982

Class SharedBufferTest
In class SharedBufferTest (Fig. 23.13), line 12 creates an ExecutorService to execute
the Producer and Consumer Runnable s. Line 15 creates an UnsynchronizedBuffer and as-
signs it to Buffer variable sharedLocation . This object stores the data that the Producer
and Consumer threads will share. Lines 24-25 create and execute the Producer and Con-
sumer . The Producer and Consumer constructors are each passed the same Buffer object
( sharedLocation ), so each object refers to the same Buffer . These lines also implicitly
launch the threads and call each Runnable 's run method. Finally, line 27 calls method
shutdown so that the application can terminate when the threads executing the Producer
and Consumer complete their tasks and line 28 waits for the scheduled tasks to complete.
When main terminates (line 29), the main thread of execution enters the terminated state.

1 // Fig. 23.13: SharedBufferTest.java

2 // Application with two threads manipulating an unsynchronized buffer.

3 import java.util.concurrent.ExecutorService;

4 import java.util.concurrent.Executors;

5 import java.util.concurrent.TimeUnit;

6
7 public class SharedBufferTest

8 {

9

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

10

{

11 // create new thread pool with two threads

12 ExecutorService executorService = Executors.newCachedThreadPool();

13
14 // create UnsynchronizedBuffer to store ints

Buffer sharedLocation = new UnsynchronizedBuffer(); 15

16
17 System.out.println(

18 "Action\t\tValue\tSum of Produced\tSum of Consumed" );

19 System.out.printf(

20 "------\t\t-----\t---------------\t---------------%n%n" );

21
22 // execute the Producer and Consumer, giving each

23 // access to the sharedLocation

24 executorService.execute( new Producer(sharedLocation));

executorService.execute( new Consumer(sharedLocation)); 25

26
27 executorService.shutdown(); // terminate app when tasks complete

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

29 }

30 } // end class SharedBufferTest

Action Value Sum of Produced Sum of Consumed
------ ----- --------------- ---------------

Producer writes 1 1

1 is lost
2 is lost

Producer writes 2 3

Producer writes 3 6

Fig. 23.13 | Application with two threads manipulating an unsynchronized buffer. ( Caution:
The example of Figs. 23.9-23.13 is not thread safe.) (Part 1 of 2.)