Slide 10.2: An inheritance example Slide 10.4: The final keyword Home

Non-Access Modifiers

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There are two kinds of modifiers:

• Access modifiers, which control the access level (described in Week 9), and
• Non-access modifiers, which do not control access level, but provide other functionality.

Non-Access Modifiers for Classes
For classes, you can use either final or abstract:

Modifier	Description
final	The class cannot be inherited by other classes.
abstract	The class cannot be used to create objects. (To access an abstract class, it must be inherited from another class.)

Non-Access Modifiers for Attributes and Methods
For attributes and methods, you can use one of the following modifiers:

Modifier	Description
final	Attributes and methods cannot be overridden/modified.
static	Attributes and methods belong to the class, rather than an object.
abstract	Can only be used in an abstract class, and can only be used on methods. The method does not have a body, for example, abstract void run( );. The body is provided by the subclass (inherited from).
transient	Attributes and methods are skipped when serializing the object containing them.
synchronized	Methods can only be accessed by one thread at a time.
volatile	The value of an attribute is not cached thread-locally, and is always read from the “main memory.”

Slide 10.2: An inheritance example Slide 10.4: The final keyword Home

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