Module definitions

Question 1

What is an OO language

Answer 1

A language which promotes or allows object oriented programming and design

Question 2

What is an object?

Answer 2

A collection of data

Question 3

What is a class?

Answer 3

Defines what an object can do

Question 4

What is a class method?

Answer 4

A static method which is associated with a class

Question 5

What is an instance method?

Answer 5

A non-static method which is associated with an object

Question 6

What is aggregation?

Answer 6

An object within an object where the inner object has a lifetime of its own

Question 7

What is the symbol for aggregation in a class diagram?

Answer 7

An empty diamond

Question 8

What is composition?

Answer 8

An object within object where the inner object lasts as long as the outer object

Question 9

What is the symbol for composition in class diagram?

Answer 9

A black filled in diamond

Question 10

What is abstraction?

Answer 10

Hides the implementation from the user for simplicity

Question 11

What is an abstract method?

Answer 11

A method without implementation (no {}) - these are placeholders for sub-classes to implement/override

Question 12

What is an abstract class?

Answer 12

A class with at least one abstract method- CANNOT create instances of the class (only references)

Question 13

What is an interface?

Answer 13

A class where every method is abstract and any data is static and final. (a class with no implementation)

Question 14

What is inheritance?

Answer 14

A class is as specialisation of another class

Question 15

What is the symbol for inheritance in a class diagram?

Answer 15

A white arrow

Question 16

How does inheritance work with classes?

Answer 16

A class extends a class

Question 17

How does inheritance work with a class and an interfaces?

Answer 17

A class implements an interface

Question 18

How does inheritance work with interfaces?

Answer 18

An interface extends an interface

Question 19

How does inheritance work with interfaces and classes?

Answer 19

DOESNT WORK THIS WAY -> a class can implement an interface not the other way round

Question 20

What is parametric polymorphism?

Answer 20

Code which works with multiple different types

Question 21

What is type erasure?

Answer 21

Type exists only at compile time and are erased before runtime

Question 22

What is ad-hoc polymorphism

Answer 22

Function overloading -> same function name but multiple different versions depending on the parameter types

Question 23

What is sub-type polymorphism?

Answer 23

Sub-classing (polymorphism in OO terms)

Question 24

What is runtime polymorphism?

Answer 24

Compiler does not know the type but looks it up at runtime

Question 25

What does it mean if a variable is final?

Answer 25

It is unchangeable (cant be changed in any implementations or extensions, both methods and classes can be final -can't change implementation or can't subclass)

Question 26

What is a design pattern?

Answer 26

A reusable solution to commonly faced problems

Question 27

What is a model-view-controller?

Answer 27

Separates data storage, presentation to user and control logic

Question 28

What is a behavioural pattern?

Answer 28

Patterns that change the behaviour of an object

Question 29

What is a strategy pattern?

Answer 29

Lets another object modify the behaviour of an object

Question 30

What is an example of a strategy pattern?

Answer 30

Layout manager

Question 31

What is an observer pattern?

Answer 31

Tell me when something happens

Question 32

What is an example of an observer pattern?

Answer 32

Button

Question 33

What is an iterative pattern?

Answer 33

Lets you iterate through contents

Question 34

What is an example of an iterative pattern?

Answer 34

For each loop! Mainclass implements class iterable, now we can have a myIterator class which implements iterator

Question 35

What is an iterable?

Answer 35

A container to iterate through

Question 36

What is an iterator?

Answer 36

Object to do the iteration

Question 37

What is a creational pattern?

Answer 37

Pattern related to the creation of objects

Question 37

What is a singleton?

Answer 37

Creates just one instance of an object and use it anywhere

Question 38

What is an example of a singleton

Answer 38

To create a constant object

Question 39

What is a simple factory?

Answer 39

Creates lots of instances of object

Question 40

What is boxing?

Answer 40

Wrapping up a data type in an object

Question 41

What is unboxing?

Answer 41

Extracting the data type again after boxing it up

Question 42

What is auto-boxing?

Answer 42

The process of wrapping a data type in an object then extracting the data type again

Question 43

What is an anonymous class?

Answer 43

An inner class without a name

Question 44

What is a lambda?

Answer 44

A simpler case for an anonymous class. When an inner class without a name implements an interface with one method

Question 45

What is a constructor?

Answer 45

Methods which are called to initialise new objects -> same name as the class like public main()

Question 46

What is encapsulation?

Answer 46

Grouping together methods and data in a class

Question 47

Who can view a public method?

Answer 47

Anyone

Question 48

Who can view a protected method?

Answer 48

Anything in this package and subclasses

Question 49

Who can view a package method?

Answer 49

Anything in this package

Question 50

Who can view a private method?

Answer 50

Only this class can access it

Question 51

What are the limitations of parametric polymorphism?

Answer 51

- Type erasure - Can only parametrise on a sub-class of a specific type

Question 52

How do we change something from type a to a generic type?

Answer 52

- Replace all of the data type with OBJECT - Except when we are having a parameter of type T - If a method returns a type T, type cast it before returning

Question 53

What are the two types of pattern we have?

Answer 53

- Behavioural patterns - Creational patterns

Question 54

Give examples of behavioural patterns

Answer 54

Observer, Strategy and Iterator

Question 55

Give examples of creational strategy patterns

Answer 55

Singleton and simple factory

Question 56

Why are design patterns useful in general?

Answer 56

- Simplify coding process - Enhance code maintainability - Promote code reuse