Java Reference
In-Depth Information
then the field
x
of class
Point
is no longer hidden within class
Test
. Within instance
methods in the declaration of class
Test
, the simple name
x
now refers to the field de-
clared within class
Point
. Code in class
Test
may still refer to that same field as
super.x
.
The expression
sample.x
still refers to the field
x
within type
Test
, but that field is now
an inherited field, and so refers to the field
x
declared in class
Point
. The output from
this variant program is:
2 2
2 2
8.3.1.2. final Fields
A field can be declared
final
(§
4.12.4
)
. Both class and instance variables (
static
and non-
static
fields) may be declared
final
.
structor (§
8.8
) of the class in which it is declared; otherwise a compile-time error occurs.
8.3.1.3. transient Fields
Variables may be marked
transient
to indicate that they are not part of the persistent state of
an object.
Example 8.3.1.3-1. Persistence of
transient
Fields
If an instance of the class
Point
:
class Point {
int x, y;
transient float rho, theta;
}
were saved to persistent storage by a system service, then only the fields
x
and
y
would
be saved. This specification does not specify details of such services; see the specific-
ation of
java.io.Serializable
for an example of such a service.
8.3.1.4. volatile Fields
rule, to ensure that shared variables are consistently and reliably updated, a thread should
ensure that it has exclusive use of such variables by obtaining a lock that, conventionally,
enforces mutual exclusion for those shared variables.
