Object Oriented Programming

Question 1

4 Major Principles of OOP

Answer 1

• inheritance
• polymorphism
• abstraction
• encapsulation

Question 2

abstract class

Answer 2

• a class that you only inherit from
• you don’t directly instantiate from

Question 3

polymorphism

Answer 3

• The ability of a subclass to also act as an instance of its own superclass
• Ex:
  
  • Superclass -> Shape
  • Subclasses-> Squares, Triangles
  • You can create an array of shapes and safely fill it with squares and triangles
• Every triangle/square/circle is also a shape

Question 4

encapsulation

Answer 4

• the process of hiding information pertaining to an object from the client

Question 5

UML

Class Diagrams

Answer 5

• unified modeling language

3 parts

• class name
• attributes
  
  • visibility - name - colon - datatype
• method
  
  • visibility - name - parens - args - colon - return type

Question 6

OOP Design

Steps

Answer 6

• focus on what, not how

Steps

1. Obtain/prepare textual description of problem
2. Underline nouns => classes
3. Underline adjectives => attributes
4. Underline active verbs => methods
5. Flesh out the requirements
6. Identify classes
   
   1. Underline nouns
7. Identfy attributes
   
   1. Underline adjectives
   2. Use domain knowledge
8. Identify oeprations
   
   1. Underline active verbs
   2. Examine interactions among entities
9. Identify major entities
10. Define bahaviors (methods) for each major entity
11. Identity sub-entities
12. Define behaviors for each sub-entity
13. Define relationships between entitties

Question 7

interaction between objects

Answer 7

3 main types

1. x uses (depends on) y: dependency
2. x has y: association/aggregation/composition:
3. x is a y: generalization (inheritance)

Question 8

association

Answer 8

• a type of OOP relationship
• a Has-a relationship
• two objects have a relationship, but they can exist independently of each other
• there is no ownership or lifetime dependency
• ex: doctor and patient
• Notation
  
  • Solid line
  • Describe relation with text

Question 9

aggregation

Answer 9

• a type of OOP relationship
• a ‘Has-a’ relationship
• A special type of association which describes a whole and its parts
• The parts can exist ouside of the whole
• ex: a baseball team and players
• Notation
  
  • Solid lne, open diamond
  • Part to whole

Question 10

composition

Answer 10

• a type of OOP relationship
• a ‘has a’ relationship
• there is ownership
• when owner is destroyed, child is destroyed
• both ownership and lifetime dependency
• ex: house and room
• ex: class and inner class
• Notation:
  
  • Solid line, closed diamond
  • Part to whole

Question 11

generalization

Answer 11

• a type of OOP relationship
• an ‘IS-a’ relationship
• basically inheritance
• Notation:
  
  • solid line, open triangle
  • subclass to superclass

Question 12

dependency

Answer 12

• x uses y
• if y changes, x might change