The result from the code below is correct but the display of the output is (to me) odd. Here is the code:
clear[A, B];
J[x_, t_] := \[HBar]/m Im[Conjugate[\[CapitalPsi][x, t]]*(\!\(
\*SubscriptBox[\(\[PartialD]\), \(x\)]\(\[CapitalPsi][x, t]\)\))]
\[CapitalPsi][x_, 0] := A E^(I k x) + B E^(-I k x)
FullSimplify[ComplexExpand[J[x, 0], {A, B}]] // TraditionalForm
the output is displayed as:
(k \[HBar] (\[LeftBracketingBar]A\[RightBracketingBar]^2-B B^\[Conjugate]))/m
or 
Why does it display the norm squared for A and B differently?
