code: public double get(int i, int j) {
  
  		if (i < 0 || i >= N) throw new IllegalArgumentException("Illegal index " + i + " should be > 0 and < " + N);
  		if (j < 0 || j >= N) throw new IllegalArgumentException("Illegal index " + j + " should be > 0 and < " + N);
  
  		return rows[i].get(j);
  	}
docs: access a value at i,j
  
  @param i
  @param j
  @return return A[i][j]