PingPong synchronization with main thread in several programming languages

main.cpp

/*
Ping pong threads in c++ by Ivan Djurdjevac
Run this code with g++ 4.x
Command is: 
g++ -std=c++0x -pthread main.cpp
Read output with
./a.out
/**/
 
 
#include <iostream>
#include <thread>
using namespace std;

// Ping pong function for thread
void ping_pong(string name) {
	for (int i = 0; i < 3; ++i) {
		std::cout << name << "\n" << std::endl;
		std::this_thread::sleep_for(std::chrono::seconds(1));
	}
}

int main() {
	std::thread ping_t, pong_t;

	std::cout << "Ready… Set… Go!\n";

	//Launch ping and pong threads
	ping_t = std::thread(ping_pong, "Ping!");
	pong_t = std::thread(ping_pong, "Pong!");
	
	ping_t.join();
	pong_t.join();
	
	std::cout << "Done!\n";
	return 0;
}

PingPong.java

class PingPongThread extends Thread {
	
	/**
	 * Message for print
	 */
	private String message;

	/**
	 * Main Application thread
	 */
	private Thread program;

	/**
	 * Counter for active running threads
	 */
	static int threadsRunning = 0;

	/**
	 * Create thread
	 * 
	 * @param msg Message
	 * @param main Main Application thread
	 */
	public PingPongThread(String msg, Thread main) {
		this.message = msg;
		this.program = main;

		++threadsRunning;
	}

	@Override
	public void run ()
	{
		try {
			for (int row = 1; row < 5; row++)
			{
				System.out.println (this.message);
				Thread.sleep(1000);
			}
		} catch (Exception e)
		{
			e.printStackTrace();
		} finally {
			
			// When thread don with his work decrement number of running threads
			--threadsRunning;
			
			// If there is no active threads We can notify main thread to continue
			if (threadsRunning <= 0)
				this.notifyMain();
		}
	}

	public void notifyMain() {
		synchronized (program) {
			try {
				program.notify();
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
	}
}

public class PingPong {

	public static void main(String[] args) {
		
		PingPongThread ping = new PingPongThread("Ping!", Thread.currentThread());
		PingPongThread pong = new PingPongThread("Pong!", Thread.currentThread());

		System.out.println("Ready… Set… Go!");
		ping.start();
		pong.start();
		
		waitPingPong(ping);

		System.out.println("Done!");

	}

	/**
	 * Wait until ping pong threads are done
	 * @param ping
	 */
	public static void waitPingPong(Thread ping) {
		synchronized (ping) {
			try {
				ping.wait();
			} catch (InterruptedException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
	}
}