import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

public class MultiplyMatrixMain {

	public static void main(String[] args) 
			throws InterruptedException, ExecutionException {
		// generare 2 matrici
		int size=2;
		ArrayList<ArrayList<Double>> m1 = new ArrayList<>();
		ArrayList<ArrayList<Double>> m2 = new ArrayList<>();
		
		//......
		
		//creare executor
		ExecutorService es= Executors.newFixedThreadPool(size);
		
		//creare task
		ArrayList<RowMultiplier> tasks= new ArrayList<>();
		
		for(int i=0;i<size;i++){
			RowMultiplier task= new RowMultiplier(m1,m2,i);
			tasks.add(task);
		}
		List<Future<ArrayList<Double>>> results=
				es.invokeAll(tasks);
		
		//prendere risultati
		ArrayList<ArrayList<Double>> result= new ArrayList<>();
		for (Future<ArrayList<Double>> r : results ){
			result.add(r.get());
		}
		
		printMatrix(result);
		
	}

	private static void printMatrix(ArrayList<ArrayList<Double>> result) {
		//...
		
	}

}