Holds if this nested type is static.
A nested type is static either if it is explicitly declared as such
using the modifier
static, or if it is implicitly static
because one of the following holds:
- it is a member type of an interface,
- it is a member interface, or
- it is a nested enum type.
See JLS v8, section 8.5.1 (Static Member Type Declarations), section 8.9 (Enums) and section 9.5 (Member Type Declarations).