Page 320 - Computer_Science_F5

is declared and initialised within methods to access the value of
the method and destroyed when the various kinds of methods. In the
method has completed. above example, methods are such

(b) Instance variables: These are as barking(), hungry() and sleeping(). Chapter Five: Object oriented programming with Java
variables within a class but is outside
FOR ONLINE READING ONLY
any method. They are initialised Class and instance in Java
when the class is instantiated. They A class is a group of items of the same
can be accessed from inside any kind. As shown in Table 5.1, a class is
method, constructor or blocks of that a three-compartment box that contains
specific class. data and operations.
(c) Class variables: These variables have
the static keyword applied and are Table 5.1: Class structure
declared inside a class, independent Class Name
of any methods. Static Attributes
A class can have any number of Dynamic Behaviors

Table 5.2 shows an example of two classes “Car” and “Fruit”

Table 5.2: Example of class
Name (Identifier) Variables Methods
(Static attributes) (Dynamic behaviors)
Car Make, model, color startEngine(), accelerate(),
brake()
Fruit Name, color, taste Ripen(),rote(),isSweet

As shown from the table, a class can be viewed in three dimensions:
1. Name or identity: This is used to identify the class.
2. Variables (sometimes called attribute, state, or field): these represent the static
attributes of the class.
3. Methods: These contain the class’s dynamic behaviors, functions, and operations.

An instance, is an object built from a class (blueprint) which has all the characteristics
defined in the class, but with specific values. For example, we can define a class
called “Car” and create three instances of the class, “Car” for “Nissan”, “Toyota”
and “Honda”.

Table 5.3 shows three instances of the class Car, identified as “Nissan”, “Toyota”
and “Honda”.

311
Student’s Book Form Five

Computer Science Form 5.indd 311 23/07/2024 12:34