java - Is there benefit in a generified interface? -

recently in answer suggested me this:

public interface operation<r extends operationresult, p extends operationparam> {      public r execute(p param); }

is better this:

public interface operation {      public operationresult execute(operationparam param); }

i can't see benefit in using first code block on second 1 ...

given both operationresult , operationparam interfaces implementer needs return derived class anyway , seems quite obvious me.

so see reason use first code block on second 1 ?

this way can declare operation implementations return more specific result, e.g.

 class sumoperation implements operation<sumresult, sumparam>

though whether of value application depends entirely on situation.

update: of course return more specific result without having generic interface, way can restrict input parameters well.

Aleternatvie