"Good at" or "Good in" [duplicate]

Possible Duplicate:
“At” vs. “in” before verb

"He is good in painting" or "He is good at painting" — which one is correct?

Solution 1:

There's only one major case that leaps to mind where "good in" is idiomatically correct:

He is good in bed.

This can be generalized somewhat to "he is good in (location where certain stereotypical activities are performed)", like saying "he is good in the field" to mean he is good at doing the tasks that need to be done in the field.

Solution 2:

If you must choose one of them:

He is good at painting

However, you might also prefer:

He paints well.

Solution 3:

In general:

He is good in [location]

and

He is good at [activity]