public void setRandoms(int totalRows, int k){
		Random rnd = new Random();
		selected = new HashSet<Integer>();
		for(int i = 0; i<k; i++){
			int rowNumber = rnd.nextInt(totalRows);
			while(selected.contains(rowNumber)){
				rowNumber = rnd.nextInt(totalRows);
			}
			selected.add(rowNumber);
		}
	}