This is an angular momentum operator, namely the $$j$$th component of the angular momentum vector operator $$\boldsymbol{L}$$, i.e. $$L_{\text x}$$, $$L_{\text y}$$ or $$L_{\text z}$$.
Angular momentum operator is given by:$$L^2 ~=~ L_{\text x}^2 ~+~ L_{\text y}^2 ~+~ L_{\text z}^2$$
Since $$L^2$$ commutates with all angular momentum components, they have the same eigenstates.