Core Java 3: OOP OOD

Question 1

4 Pillars of OOP

Answer 1

A PIE: Abstraction, Polymorphism, Inheritance, and Encapsulation.

Question 2

Abstraction

Answer 2

hiding complex code from user; user is only concerned with inputs/outputs, don’t need to worry about internal components; abstraction creates reusable/discrete modules; write something once and use it anywhere to fulfill task in application; single task as a method; group of tasks as class; group of related classes as layer.

Question 3

Polymorphism

Answer 3

• ability to give different definitions for performing a task (OVERLOADING & OVERRIDING).
• Overloading: ability to give a definition for a method which takes different arguments; early-binding, compile-time, static binding.
• Overriding: define child-specific implementation of parent method. Child method needs to perform same overall function (not overriding if child is violating intent of parent); late-binding, runtime, dynamic binding.

Question 4

Inheritance

Answer 4

• Ability to set parent-child relationships between classes
• all attributes and behaviors of parent are accessible to child.
• Code reuse: define attributes & methods in parent, any number of children can reuse definitions.
• Extensibility: can use abstract parent as dependency to implement concrete child.

Question 5

Encapsulation

Answer 5

maximizing cohesion by grouping related elements together; wrap cohesive elements together, protect access by making them private, limit access via getters/setters so you have precise control over how data stored/retrieved

Question 6

Cohesion

Answer 6

togetherness; extent to which elements of code belong together.

Question 7

Coupling

Answer 7

measurement of dependency between classes; if I change sth. in class A, does it break functionality in class B?