J = 2: “parallel and same direction” because adding 2 vectors with same direction (and same magnitude) will result in the largest possible vector.
J = 0; “parallel and opposite direction” because adding 2 vectors with opposite direction (and same magnitude) will result in smallest possible vector, the zero vector.
J = 1; “perpendicular to each other” because from the pythagoras theorem the resulting vector will have a magnitude between that of 0 and 2.