The Java Language Specification, Third Edition

CLASSES Field Modifiers 8.3.1
of accessing the origin class variable access the same object, evidenced by the
fact that the value of the reference equality expression (§15.21.3):
q.origin==Point.origin
is true. Further evidence is that the incrementation:
p.origin.useCount++;
causes the value of q.origin.useCount to be 1; this is so because p.origin and
q.origin refer to the same variable.
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.
It is a compile-time error if a blank final (§4.12.4) class variable is not definitely
assigned (§16.8) by a static initializer (§8.7) of the class in which it is
declared.
A blank final instance variable must be definitely assigned (§16.9) at the end
of every constructor (§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.
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 specification of java.io.Serializable for an example of such a service.
8.3.1.4 volatile Fields
DRAFT
As described in §17, the Java programming language allows threads to access
shared variables. As a 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.
The Java programming language provides a second mechanism, volatile
fields, that is more convenient than locking for some purposes.
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