Option D

Question 1

Outline the general nature of an object.

Answer 1

In general an object can be defined as a location in memory having a value. This could be a variable or data structure. Usually when talking about objects it refers to instances of a class.

Question 2

What are the three rows of a UML diagram?

Answer 2

1. Class name
2. Variables
3. Methods

Question 3

What is the structure of a variable in a UML diagram?

Answer 3

varName : type ( = value)

Question 4

What are the three types of relationships between objects?

Answer 4

The three types of relationships that should be known are dependency (“uses”), aggregation (“has a”) and inheritance (“is a”).

Question 5

Explain aggregation.

Answer 5

Aggregation is a type of relationship between objects. It means that one type of object contains another or is composed of another. Some examples are: a car has-an engine, a bicycle has-a wheel, and a coffee cup has coffee.

Question 6

Explain inheritance.

Answer 6

Inheritance is a type of relationship between objects. It means that one type of object is a more specific version of a general type. Some examples are: a car is-a vehicle, a bicycle is-a vehicle, and a coffee cup is-a cup.

Question 7

Explain dependency.

Answer 7

Dependency is a type of relationship between objects. It means that during some activity, one type of object uses another type of object. Some examples are: a car uses-a squeegee (during a window-washing activity), a bicycle uses-a pump (during a tire-pumping activity), and a coffee cup uses-a stirrer (during a stirring activity).

Question 8

How are dependency and aggregation represented in a UML diagram with multiple classes?

Answer 8

In UML:
A dependency (when one dies, the other dies) is represented by a shaded diamond

An aggregation is represented by a hollow diamond

Question 9

What are the two parts of an object?

Answer 9

1. Attributes (variable names)

2. Behaviour (Methods)

Question 10

What are the four fundamental OOP concepts?

Answer 10

1. Encapsulation
2. Abstraction
3. Inheritance
4. Polymorphism

Question 11

Encapsulation and abstraction are _____ concepts.

Answer 11

Complementary

Question 12

What’s the major difference between abstraction and encapsulation?

Answer 12

Just like abstraction, encapsulation hides data, but at a deeper level.

Question 13

What is encapsulation?

Answer 13

Encapsulation is the process of combining data and methods into a single unit (class). In Encapsulation, the data is not accessed directly; it is accessed through the methods present inside the class. In simpler words, attributes of the class are kept private and public getter and setter methods are provided to manipulate these attributes. Thus, encapsulation makes the concept of data hiding possible.

Question 14

What is inheritance?

Answer 14

Inheritance enables programmers to define an “is-a” relationship between a class and a more specialized version of that class. For example, if a Student class extends a Person class, then it should be the case that Studentis-aPerson. The subclass Student builds on the functionality of the superclass Person.

Question 15

If a parent class is shapes, list some child classes it can have?

Answer 15

triangle, rectangle etc.

Question 16

What is polymorphism? What are the two types?

Answer 16

Polymorphismrefers to a programming language’s ability to process objects differently depending on their data type or class. The two types are method overloading and method overriding.

Question 17

Describe method overriding.

Answer 17

Method overriding is a type of polymorphism that allows a subclass or child class to provide a specific implementation of amethodthat is already provided by one of its superclasses or parent classes. Method overriding allows a sub class to use all the general definitions that a super class provides and add specialised definitions through overridden methods.

Question 18

Describe method overloading.

Answer 18

Method overloadingis a type of polymorphism that allows a class to have two or moremethodshaving same name, if their argument lists are different. Method overloading allows methods that perform similar or closely related functions to be accessed through a common name.

Question 19

What is the main advantage of encapsulation?

Answer 19

The main benefit of encapsulation is the ability to modify our implemented code without breaking the code of others who use our code. With this feature, encapsulation gives maintainability, flexibility and extensibility to our code.

Question 20

List 3 advantages of inheritance.

Answer 20

1. Reusability - ability to use public methods of base class without rewriting the same
2. Extensibility - extending the base class logic as per business logic of the derived class
3. Data hiding - base class can decide to keep some data private so that it cannot be altered by the derived class
4. Space saving

Question 21

List 2 advantages of polymorphism

Answer 21

1. Method overloading can be used so that we do not have to find alternative and meaningful names for two methods that perform the same things with slight differences (e.g. different data types)
2. Method overriding works together with inheritance to enable code reuse of existing classes without the need for re-compilation.

Question 22

What are libraries?

Answer 22

Pre-defined sets of codes that could be used.

Question 23

Why are libraries useful?

Answer 23

The main advantage of using libraries of objects is so that sorts and other complex algorithms and processes do not have to be “re-invented”, thus saving time.

Question 24

List 3 disadvantages of OOP.

Answer 24

1. May not be useful for very simple procedures
2. Larger file size
3. Slower
4. Steep learning curve

Question 25

List 6 advantages of modularity

Answer 25

• If a single procedure is developed it can be reused multiple times without having to retype the code (reusability)
• Programs can be designed more easily and more effectively due to the divisions of the entire code into sectors because a small team deals with only a small part of the entire code (focus)
• Modular programming allows many programmers to collaborate on the same application (team management)
• Code is short, simple and easier to understand (readability)
• Scoping of variables can be easily controlled (code management)
• When errors are localized to a subroutine or function, they can be easily identified (debugging)

Question 26

What is a class?

Answer 26

a blueprint or template for objects

Question 27

What is an identifier?

Answer 27

namesof variables, methods, classes, packages and interfaces etc.

Question 28

What are primitive data types?

Answer 28

Types of data that are predefinedin the programming language

Question 29

What is an instance variable?

Answer 29

avariabledefined in a class (i.e. a membervariable), for which each instantiated object of the class has a separate copy, orinstance

Question 30

What is a local variable?

Answer 30

variables declared in methods or blocks and is destroyed when the program exits the block

Question 31

What is a method?

Answer 31

a sub-procedure/sub-program in java that forms part of a class/object

Question 32

What is an accessor?

Answer 32

a method used to get/return some properties of an object (used in encapsulation to get value of private variable)

Question 33

What is a mutator?

Answer 33

a method used to change properties of an object (used in encapsulation)

Question 34

What is a signature?

Answer 34

the method signature contains the parameters and names of a method, used to distinguish between two methods with the same name in polymorphism

Question 35

What does the “private” keyword do?

Answer 35

signals that only visible in the class it’s in

Question 36

What does the “public” keyword do?

Answer 36

signals that visible in all classes

Question 37

What does the “protected” keyword do?

Answer 37

signals that only visible in the class it’s in and any subclasses

Question 38

What does the “extends” keyword do?

Answer 38

signals the creation of subclass

Question 39

What does the “static” keyword do?

Answer 39

signals that the variable or function is shared between all instances of that class not to the object itself