About Programation

Central Principles in POO

Abstraction

• Abstraction is a process of hiding the implementation details from the user. Оnly the functionality will be provided to the user.
• Related to both encapsulation and data hiding
• My words:
  • One abstract method = class abstract.
  • This class can be extends by other classes
  • The child classes will contain the extended methods of the abstract class, they can use them and the declaration of the abstract one
  • The abstract method will be over-writed to have the possibility to write a different code for each child

Inheritance

• Extends: Multiple inheritance
• Using extends keyword, the child class inherits the methods of parent class.

Encapsulation

• Declare private variables
• Declare Setters and Getters to modify them

Polymorphism

• Process objects differently based on their data type.
• One method with multiple implementation
• This can be implemented by designing a generic interface, which provides generic methods for a certain class of action and there can be multiple classes, which provides the implementation of these generic methods.
• Ways to do it:
  • Override: method of an extended class
  • Compile Time: Multiple methods declaration with multiple parameters
• In polymorphism, the parent class has a declared method wich is not abstracted and not empty. There is a process inside, it is not only a declaration in a abstract class

Packages

• Prevent naming conflicts
• Control access
• Make searching/locating and usage of classes, interfaces, enumerations and annotations easier...

Interface

• Collection of abstract methods.
• A class implements an interface, thereby inheriting the abstract methods of the interface.

Difference Controller and Presenter

• Presenter
  • The View is responsible for handling the UI events
• Controller
  • Handle the UI Events

Design Patterns

• MVC
• MVP
• MVVM

Famous Patterns

Singleton

• Class Singleton with a private constructor
  • Private static parameter single_instance set to null
  • Private static Method getInstance(): if the parameter is null, instantiate Singleton class as New, if not return the existing instance returning the parameter single_instance

Every instantiation has to be called as: Singleton.getInstance();

Observable

• to fill

Paradigm

• REST: Representational State Transfer; Used with Web Services
• Object
• Procedural

Acronyms

• CRUD: Create, Read, Update, Delete

More

• Java