Java Reference
In-Depth Information
applications, to avoid problems at a later time. Someone who later uses
the class directly or extends the class may assume the existence of a valid
toString
method.
SR 9.22
The
final
modifier can be applied to a particular method, which
keeps that method from being overridden in a child class. It can also be
applied to an entire class, which keeps that class from being extended
at all.
9.6
The Component Class Hierarchy
SR 9.23
a. True, b. True, c. False, d. False, e. False, f. True
SR 9.24
The benefits include not having to worry about the details of applet
creation and execution, or how the applet interacts with the browser, or
security concerns. Essentially, you do not have to worry about anything
that would be a common concern across all applets; such concerns have
already been handled. You just have to worry about what makes your
applet different from other applets.
9.7
Extending Adapter Classes
SR 9.25
An adapter class is a class that implements a listener interface, providing
empty definitions for all of its methods. A listener class can be created
by extending the appropriate adapter class and overriding the methods
of interest.
SR 9.26
The
OffCenterPanel
class extends the
JPanel
class. The
JPanel
class inherits from all of the other classes mentioned. Therefore,
an
OffCenterPanel
object “is” a
JPanel
, and a
JComponent
, and a
Container
, and an
Object
.
SR 9.27
The
OffCenterListener
class extends the
MouseAdapter
class. Since the
MouseAdapter
class includes methods for each of the mouse events, the
OffCenterListener
class inherits those methods and does not need to
define them directly.
9.8
The
Timer
Class
SR 9.28
An object created from the
Timer
class produces an action event at
regular intervals. It can be used to control the speed of an animation.
SR 9.29
The
Timer
constructor is called in the
ReboundPanel
constructor to set
the initial delay and to associate a listener with the timer. The
start
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