public class Barrier {
	
	final int NBR_ELEMENTS = 4;
	final int NBR_ITERATIONS = 30;
	int[] data = new int[NBR_ELEMENTS];

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		Barrier barrier = new Barrier();
		barrier.initializeData();
		barrier.testBarrier();
		//barrier.showData();
		// TODO Auto-generated method stub
	}
	
	public void testBarrier() {
		for (int i = 0; i < NBR_ELEMENTS; ++i) {
			final int I = i;
			Thread t = new Thread() {
				public void run() {
					for (int j = 0; j < NBR_ITERATIONS; ++j) {
						data[I] = data[I] + 1;
						barrier();
					}
				}
			};
			t.start();
		}
	}
	
	public void initializeData() {
		for (int i = 0; i < NBR_ELEMENTS; ++i)
			data[i] = i;
	}
	
	public void showData() {
		for (int i = 0; i < NBR_ELEMENTS; ++i)
			System.out.print(data[i]+" ");
		System.out.println();
	}
	
	int nbrWaiting = 0;
	synchronized void barrier() {
		nbrWaiting++;
		if (nbrWaiting == NBR_ELEMENTS) {
			showData();
			nbrWaiting = 0;
			notifyAll();
		}
		else {
			try {
				wait();
			} catch (InterruptedException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
	}

}