can someone plz help me about this uml statement.

+setCourse(type:char,desc:String):void The type can either be ‘n’,’N’,’D’,’d’. Any other type is invalid. If the type is either ‘n’ or ‘N’ then parameter desc (which MUST have a length>0) will be assigned to the property courseNum. If the type is either ‘d’ or ‘D’ then the parameter desc (which must have length>0) is assigned to the courseDesc. If the type is not any of ‘d’, ‘D’,’n’,’N’, simply exit the method without making ANY changes at all.