Table 3-2. Java modifiers
|
Modifier
|
Used on
|
Meaning
|
|---|
|
abstract
|
Class
|
The
class contains unimplemented methods and cannot be instantiated.
|
| |
Interface
|
All interfaces are
abstract. The modifier is optional in interface
declarations.
|
|
abstract
|
Method
|
No
body is provided for the method; it is provided by a subclass. The
signature is followed by a semicolon. The enclosing class must also
be abstract.
|
|
final
|
Class
|
The class cannot be subclassed.
|
| |
Method
|
The method cannot be overridden (and is not subject to dynamic method
lookup).
|
| |
Field
|
The field cannot have its value changed. static
final fields are compile-time constants.
|
| |
Variable
|
A local variable, method parameter,
or exception parameter cannot have its value changed. Useful with
local classes.
|
|
native
|
Method
|
The
method is implemented in some platform-dependent way (often in C). No
body is provided; the signature is followed by a semicolon.
|
|
None (package)
|
Class
|
A
non-public class is accessible only in its
package.
|
| |
Interface
|
A non-public interface is accessible only in its
package.
|
| |
Member
|
A member that is not private,
protected, or public has
package visibility and is accessible only within its package.
|
|
private
|
Member
|
The member
is accessible only within the class that defines it.
|
|
protected
|
Member
|
The
member is accessible only within the package in which it is defined
and within subclasses.
|
|
public
|
Class
|
The class is
accessible anywhere its package is.
|
| |
Interface
|
The interface is accessible anywhere its package is.
|
| |
Member
|
The member is accessible anywhere its class is.
|
|
strictfp
|
Class
|
All methods of the class are implicitly strictfp.
|
|
strictfp
|
Method
|
All floating-point computation done
by the method must be performed in a way that strictly conforms to
the IEEE 754 standard. In particular, all values, including
intermediate results, must be expressed as IEEE
float or double values and
cannot take advantage of any extra precision or range offered by
native platform floating-point formats or hardware. This modifier is
rarely used.
|
|
static
|
Class
|
An inner
class declared static is a top-level class, not
associated with a member of the containing class.
|
| |
Method
|
A
static method is a class method. It is not passed
an implicit this object reference. It can be
invoked through the class name.
|
| |
Field
|
A static
field is a class field. There is only
one instance of the field, regardless of the number of class
instances created. It can be accessed through the class name.
|
| |
Initializer
|
The
initializer is run when the class is loaded rather than when an
instance is created.
|
|
synchronized
|
Method
|
The
method makes nonatomic modifications to the class or instance, so
care must be taken to ensure that two threads cannot modify the class
or instance at the same time. For a static method,
a lock for the class is acquired before executing the method. For a
non-static method, a lock for the specific object
instance is acquired.
|
|
TRansient
|
Field
|
The
field is not part of the persistent state of the object and should
not be serialized with the object. Used with object serialization;
see java.io.ObjectOutputStream.
|
|
volatile
|
Field
|
The
field can be accessed by unsynchronized threads, so certain
optimizations must not be performed on it. This modifier can
sometimes be used as an alternative to
synchronized. This modifier is very rarely used.
|
