Java Reference
In-Depth Information
Summary of Key Concepts
The heart of object-oriented programming is defining classes that represent
objects with well-defined state and behavior.
■
The scope of a variable, which determines where it can be referenced,
depends on where it is declared.
■
A UML class diagram helps us visualize the contents of and relationships
among the classes of a program.
■
An object should be encapsulated, guarding its data from inappropriate
access.
■
Instance variables should be declared with private visibility to promote
encapsulation.
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Most objects contain accessor and mutator methods to allow the client to
manage data in a controlled manner.
■
The value returned from a method must be consistent with the return type
specified in the method header.
■
When a method is called, the actual parameters are copied into the formal
parameters.
■
A variable declared in a method is local to that method and cannot be
used outside of it.
■
A constructor cannot have any return type, even
void
.
■
A GUI is made up of components, events that represent user actions, and
listeners that respond to those events.
■
Listeners are often defined as inner classes because of the intimate relation-
ship between the listener and the GUI components.
■
Exercises
Visit
www.myprogramminglab.com
to complete many of these Exercises
online and get instant feedback.
EX 4.1
For each of the following pairs, which represents a class and
which represents an object of that class?
a. Superhero, Superman
b. Justin, Person
c. Rover, Pet
d. Magazine, Time
e. Christmas, Holiday
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