Java Reference
In-Depth Information
variables and parameters.
Example 4-4
illustrates the different kinds of fields and
variables that may be accessible to a local class:
Example 4-4. Fields and variables available to a local class
class
A
{
protected
char
a
=
'a'
;
}
class
B
{
protected
char
b
=
'b'
;
}
public
class
C
extends
A
{
private
char
c
=
'c'
;
// Private fields visible to local class
public
static
char
d
=
'd'
;
public
void
createLocalObject
(
final
char
e
)
{
final
char
f
=
'f'
;
int
i
=
0
;
// i not final; not usable by local class
class
Local
extends
B
{
char
g
=
'g'
;
public
void
printVars
()
{
// All of these fields and variables are accessible to this class
System
.
out
.
println
(
g
);
// (this.g) g is a field of this class
System
.
out
.
println
(
f
);
// f is a final local variable
System
.
out
.
println
(
e
);
// e is a final local parameter
System
.
out
.
println
(
d
);
// (C.this.d) d field of containing class
System
.
out
.
println
(
c
);
// (C.this.c) c field of containing class
System
.
out
.
println
(
b
);
// b is inherited by this class
System
.
out
.
println
(
a
);
// a is inherited by the containing class
}
}
Local
l
=
new
Local
();
// Create an instance of the local class
l
.
printVars
();
// and call its printVars() method.
}
}
m
e
Lexical Scoping and Local Variables
A local variable is defined within a block of code that defines its
scope
, and outside
of that scope, a local variable cannot be accessed and ceases to exist. Any code
within the curly braces that define the boundaries of a block can use local variables
defined in that block.
This type of scoping, which is known as
lexical scoping
, just defines a section of
source code within which a variable can be used. It is common for programmers to
think of such a scope as
temporal
instead—that is, to think of a local variable as
existing from the time the JVM begins executing the block until the time control
exits the block. This is usually a reasonable way to think about local variables and
their scope.
