SOURCE CODE

import java.applet.Applet;
import java.awt.*;

public class SharedCell2 extends Applet {
	// show multiple threads modifying shared objects.
	// Use synchronization to ensure that both threads access the shared cell properly

	private TextArea output;

	public void init()
	{
		output = new TextArea (28, 48);
		add (output);
	}

	public void start ()
	{
		HoldInteger h = new HoldInteger( );
		ProduceInteger p = new ProduceInteger(h, output );
		ConsumeInteger c = new ConsumeInteger(h, output );

		p.start();
		c.start();
	}
}

class ProduceInteger extends Thread
{
	private HoldInteger pHold;
	private TextArea output;

	public ProduceInteger ( HoldInteger h, TextArea out)
	{
		pHold = h;
		output = out;
	}

	// execute the thread
	public void run()
	{
		for ( int count = 0; count < 10; count++)
		{
				pHold.setSharedInt( count);
				output.appendText ("\n Producer set sharedInt to " + count );
		// put thread to sleep for a random interval
			try
			{	sleep( (int) (Math.random() * 3000 ) ); }
			catch ( InterruptedException exception )
			{	System.err.println ("Exception: " + exception.toString() );	}
		}
	}
}
class ConsumeInteger extends Thread
{
	private HoldInteger cHold;
	private TextArea output;


	public ConsumeInteger ( HoldInteger h, TextArea out)
	{
		cHold = h;
		output = out;
	}

	// execute the thread
	public void run()
	{
		int val;
		
		val = cHold.getSharedInt();
		output.appendText ("\n Consumer retrieved " + val );
		while ( val != 9)
		{
		// put thread to sleep for a random interval
			try
			{	sleep( (int) (Math.random() * 3000 ) ); }
			catch ( InterruptedException exception )
			{	System.err.println ("Exception: " + exception.toString() );	}
			val = cHold.getSharedInt();
			output.appendText ("\n Consumer retrieved " + val );
		}
	}
}

class HoldInteger 
{
//objects of this class are monitors

	private int sharedInt;
	private boolean writeable = true;  // monitor's condition variable

	public synchronized void setSharedInt (int val ) 
	{ 
		while ( !writeable )
		{
			try 
			{ wait(); }
			catch ( InterruptedException exception )
			{	System.err.println ("Exception: " + exception.toString() );	}
		}
		sharedInt = val; 
		writeable = false;
		notify();
	}
	
	public synchronized int getSharedInt () 
	{ 
		while ( writeable )
		{
			try 
			{ wait(); }
			catch ( InterruptedException exception )
			{	System.err.println ("Exception: " + exception.toString() );	}
		}
		writeable = true;
		notify();
		return sharedInt; 
	}
}