Page 363 - Computer_Science_F5

Computer Science 1. Write a Java class ‘Car’ with
Exercise 5.3
a constructor that initialises
the ‘brand’ and ‘model’
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attributes. Demonstrate its
usage in a ‘Main’ class.
2. Create a class ‘Book’ with
attributes ‘title’, ‘author’,
and ‘price’. Implement a
parameterised constructor
that initialises these attributes.
Write a ‘Main’ class to create
and display details of multiple
‘Book’ objects.
3. Define a class ‘Employee’
with attributes ‘name’ and
‘salary’. Include a default
constructor that initialises
name to “Unknown” and
‘salary’ to 0. Demonstrate
creating an ‘Employee’ object
using this default constructor
in a ‘Main’ class.
4. Discuss the concept of
destructors in Java. Explain
why Java does not have a
‘finalize’ method like C++
and how garbage collection
handles resource cleanup.
5. Create a class
‘DatabaseConnection’
that simulates opening a
database connection in its
constructor and closing it in a
method ‘closeConnection()’.
Illustrate the importance of
proper resource management
using constructors and
methods in Java.
Computer Science Form 5.indd 354
Implementation of key OOP features
in Java
The implementation of key OOP features in
Java, including inheritance, encapsulation,
polymorphism, and abstraction, enables
developers to create modular and reusable
code. These principles help build robust,
scalable, and maintainable applications.
Inheritance in Java
Java allows to borrow (inherit) features
from one class to create a new class. Using
inheritance, you can create a general class
that defines traits common to a set of related
items. This class can then be inherited by
other, more specific classes, each adding
those things that are unique to it. This
inheritance concept has two key players:
(a) The “Child” class (Subclass): This class
inherits properties and methods from
another class.
(b) The “Parent” class (Superclass): This
is the class whose features are being
inherited. The child class inherits all of
the variables and methods defined by
the superclass and adds its own, unique
elements.
(a) Declaration in inheritance
To declare a superclass, the class keyword
followed by the class name is used. Then
the superclass with its fields and methods
is declared. To declare a subclass, the class
keywords followed by the subclass name,
then, the extends keyword followed by the
superclass name is used as shown in Figure
5.22. In order to inherit the features, that is,
the new class to inherit from the existing
class, the “extends” keyword is used.
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