Lab 5: Monitors and Thread Synchronization 1

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Concurrent Programming with Java
Lab Manual, Version 1.0, F. Astha Ekadiyanto, 2002.

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Lab 5: Monitors and Thread Synchronization 1

Race Condition
Observing simple thread synchronization using Monitor Demonstration
Consumer Producer synchronization scenario Demonstration

Consumer-Producer synchronization scenario Demonstration

All the codes and materials in this section are taken from http://www.hta-be.bfh.ch/~fischli/kurse/threads/prodcons/index.html

The figure above describes the Consumer-Producer scenario. Each person in the figure represents a single thread either as a Producer (green color) or as a Consumer (blue color).

The roles are:

The Producer threads are to produce objects and put them in a shared Buffer (an Array or a Vector).
In this scenario we must assume that the Buffer has limited size (which is mostly the case in the real world). When the Buffer is full, the Producer must wait until there are some space available before writing into it.
The Consumer threads are to consume objects from the Buffer. Whenever there are objects available in the Buffer, any Consumer can read from it and thus consume the object. If there are no objects available (either nothing has been produced, or all have been consumed), the "starving" Consumer must wait until it is available.

Thus, the Producer and Consumer must have three consecutive states which are:

	Sleeping (Doing some other process)	Waiting (Trying to access Buffer)	Consuming (After Accessing Buffer)
Consumer	cons0.gif	cons2.gif	cons1.gif
	Sleeping (Doing some other process)	Producing (About to access Buffer)	Waiting (Trying to access Buffer)
Producer	prod0.gif	prod1.gif	prod2.gif
Cartoons by Mackie G. Majcher

Now let us implement the codes. First of all, create a new BlueJ Project called ConsProd. Then inside the ConsProd directory create another directory called img (this will be the place to store all the animation images). Get the images zip file (consprod.zip) and extract the in the Path to ConsProd\img\ directory. Then, create the following classes:

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