Java_Synchronized.java

// A Java program to demonstrate working of
// synchronized.
import java.io.*;
import java.util.*;

// A Class used to send a message
class Sender
{
	public void send(String msg)
	{
		System.out.println("Sending\t" + msg );
		try
		{
			Thread.sleep(1000);
		}
		catch (Exception e)
		{
			System.out.println("Thread interrupted.");
		}
		System.out.println("\n" + msg + "Sent");
	}
}

// Class for send a message using Threads
class ThreadedSend extends Thread
{
	private String msg;
	Sender sender;

	// Receives a message object and a string
	// message to be sent
	ThreadedSend(String m, Sender obj)
	{
		msg = m;
		sender = obj;
	}

	public void run()
	{
		// Only one thread can send a message
		// at a time.
		synchronized(sender)
		{
			// synchronizing the snd object
			sender.send(msg);
		}
	}
}

// Driver class
class Java_Synchronized
{
	public static void main(String args[])
	{
		Sender snd = new Sender();
		ThreadedSend S1 =
			new ThreadedSend( " Hi " , snd );
		ThreadedSend S2 =
			new ThreadedSend( " Bye " , snd );

		// Start two threads of ThreadedSend type
		S1.start();
		S2.start();

		// wait for threads to end
		try
		{
			S2.join();
			S1.join();
		}
		catch(Exception e)
		{
			System.out.println("Interrupted");
		}
	}
}

/* 
// An alternate implementation to demonstrate
// that we can use synchronized with method also.
class Sender
{
	public synchronized void send(String msg)
	{
		System.out.println("Sending\t" + msg );
		try
		{
			Thread.sleep(1000);
		}
		catch (Exception e)
		{
			System.out.println("Thread interrupted.");
		}
		System.out.println("\n" + msg + "Sent");
	}
}
*/

/* 
// One more alternate implementation to demonstrate
// that synchronized can be used with only a part of
// method
class Sender
{
	public void send(String msg)
	{
		synchronized(this)
		{
			System.out.println("Sending\t" + msg );
			try
			{
				Thread.sleep(1000);
			}
			catch (Exception e)
			{
				System.out.println("Thread interrupted.");
			}
			System.out.println("\n" + msg + "Sent");
		}
	}
}
*/