Lecture 5 - Definining a class, attributes and methods

Question 1

What is a class ?

Answer 1

A collection of similar
objects.

A class is a template or blueprint of objects of the same kind

Instances of a class are
objects

Question 2

What is object oriented Programming?

Answer 2

is a programming paradigm that uses abstraction (in the form of classes and objects) to create models based on the real world environment.

Question 3

What does a object oriented program consist of ?

Answer 3

many well encapsulated objects and interacting with each other by sending messages

Question 4

Object oriented features ?

Answer 4

• Encapsulation
• Inheritance
• Polymorphism
• Abstraction

Question 5

Procedural-oriented programs:

Answer 5

focus on procedures, with function as basic unit.

Are not suitable of high-level abstraction for solving real life problems.

Question 6

Object-oriented programs:

Answer 6

focus on components that the user perceives, with objects as basic unit.

Permit higher level of abstraction for solving real-life problems.

Ease in software design, in software maintenance and reusable software.

Question 7

What does a class consist of ?

Answer 7

Attributes: (or fields) define the object’s state

Methods: define what can be done to them, i.e., object’s
behaviors

Constructors: create an object

Question 8

Naming conventions for classes:

Answer 8

mixed case, each word starting upper case

E.g., BouncingBall, HelloWorld, ParetoArchive

Question 9

Naming conventions for Methods and Attributes:

Answer 9

mixed case, lower case first letter

E.g., width, originX, borrowDate

E.g., brake, addValueToArchive, resetButton

Question 10

What type of attributes are there ?

Answer 10

Instance attributes: belongs to objects.

Static attributes: belongs to the class. refers the common property of all objects (that is not unique
for each object) e.g. company name of employees. Through static keywords.
static final int NUMBER OF SIDES = 4;

Question 11

What are methods ?

Answer 11

Methods are well-defined sets of instructions to perform a specific
task.

In a method you have :
Input data: known as method parameters or arguments

Output data: through return statement.
if the return type is void, no need to return.

Question 12

What can a method access?

Answer 12

all of that class’s attributes (static and instance)
local variables

the parameters passed to it
variables declared within the method itself

Question 13

What is method overloading :

Answer 13

two/more methods

share the same name, but with different method arguments.

Question 14

What can methods be divided into:

Answer 14

Instance methods: belongs to objects.

Static methods: belongs to the class:
The main() method is a static method.
Through static keywords.