Java Reference
In-Depth Information
Furthermore, if there exists a supertype
X
of
T
, and a supertype
Y
of
S
, such that
both
X
and
Y
are provably distinct parameterized types (§
4.5
), and that the erasures
of
X
and
Y
are the same, a compile-time error occurs.
• If
T
is an interface type:
pertype
Y
of
S
, such that both
X
and
Y
are provably distinct parameterized
types, and that the erasures of
X
and
Y
are the same, a compile-time error oc-
curs.
Otherwise, the cast is always legal at compile time (because even if
S
does not
implement
T
, a subclass of
S
might).
occurs.
• If
T
is a type variable, then this algorithm is applied recursively, using the upper
bound of
T
in place of
T
.
• If
T
is an array type, then
S
must be the class
Object
, or a compile-time error occurs.
If
S
is an interface type:
• If
T
is an array type, then
S
must be the type
java.io.Serializable
or
Cloneable
(the only
interfaces implemented by arrays), or a compile-time error occurs.
supertype
Y
of
S
, such that both
X
and
Y
are provably distinct parameterized types,
and that the erasures of
X
and
Y
are the same, a compile-time error occurs.
Otherwise, the cast is always legal at compile time (because even if
T
does not im-
plement
S
, a subclass of
T
might).
• If
T
is a type that is
final
, then:
♦ If
S
is not a parameterized type or a raw type, then
T
must implement
S
, or a
compile-time error occurs.
♦ Otherwise,
S
is either a parameterized type that is an invocation of some gener-
ic type declaration
G
, or a raw type corresponding to a generic type declaration
G
. Then there must exist a supertype
X
of
T
, such that
X
is an invocation of
G
,
or a compile-time error occurs.
Furthermore, if
S
and
X
are provably distinct parameterized types then a
compile-time error occurs.
If
S
is a type variable, then this algorithm is applied recursively, using the upper bound of
S
in place of
S
.
