How to use global variables with multiple threads

public class main{


	public static int global;




	public static void main(String[] args){

			Girls [] girls = new Girls[10];


			Guys [] guys = new Guys[10];

			for(int i = 0; i < 10; i++)
			{


				girls[i] = new Girls();
				guys[i] = new Guys();

			}


			for(int i = 0; i < 10; i++)
			{

				girls[i].start();

				guys[i].start();



			}




			for(int i = 0; i < 10; i++)
			{
				try{



					girls[i].join();
					guys[i].join();



				} catch(InterruptedException e){
					System.out.println("exc caught");
				}


			}


	}
}

public class Guys extends Thread{



		public static void go()throws InterruptedException{

			final Lock lock = new ReentrantLock();



			lock.lock();


			System.out.println("global " + main.global);



			main.global = main.global + 100;

			lock.unlock();


		}






	public void run(){

		try{

		FileControl2 fic = new FileControl2();


			for(int i = 0; i <1; i++)
			{
				System.out.println(this);


				fic.GuysEntry();

				go();

				fic.GuysExit();

			}
		} catch(InterruptedException e)
		{
			System.out.println("Interrupted Exception caught");
		}

	}


}

public class FileControl2 {

	final Lock lock = new ReentrantLock();
	final Condition guys = lock.newCondition();
	final Condition girls = lock.newCondition();
	int nGirls = 0;
	int nGuys = 0;



	public void GuysEntry()throws InterruptedException{
		lock.lock();
		try{
			if(nGirls > 0)
			{
				guys.await();
			}
			nGuys++;




		   }
		finally{
			lock.unlock();
		}


	}



	public void GuysExit()throws InterruptedException{
		lock.lock();
		try{
			girls.signal();
			nGuys--;

		}
		finally{

			lock.unlock();
		}

	}


	public void GirlsEntry()throws InterruptedException{
		lock.lock();
		try{

			if(nGuys > 0)
			{
				girls.await();
			}
			nGirls++;


		}
		finally{

			lock.unlock();
		}

	}

	public void GirlsExit()throws InterruptedException{
		lock.lock();
		try{
			guys.signal();
			nGirls--;

		}
		finally{
			lock.unlock();
		}

	}


}