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Object Oriented Programming Intro.md

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Object Oriented Programming Intro

  • What is procedural programming?

    • structured programming conisists of desining set of procedure to solve a program

  • Why we use it - small problems easily resolved w/ a procedural implementation * As we get more complex, we need a more complex approach

    • drawbacks: scale poorly, as it grows in size:
      • harder to read
      • harder to de-bug
      • maintance becomes difficult
      • testing a single aspect becomes nearly impossible
      • behavior becomes tightly-coupled - the behavior of each code is tied to the previous one

  • Why we use OOP?

    • large problems can be scaled down
    • allows to view code details within the context of a specific object (i.e. game = car is an object, track is an object, seat is an object)
    • Allows you to test each individual aspect of the object and not the entire game when the code fails
    • OOP = program is made of objects
    • object has specific functionalities, which users acess via the object's methods
    • OOP paradigm suggests that a program:
      • identiy structure
      • then which item will be used

  • 3 aspect of an object

    • identiy - what is the location?
      • how is the obj distinguished from the other objects of the same type? (e.x. two same honda civic)
    • state - what does it store?
      • What is the value of the internal obj this obj contains? (i.e. two cups, differnet contents)
    • Behavior - How does it act?
      • What services or actions this object cn perform

  • Classes

    • template/blue print from which obj are mde
      • cookie cutter to a cookie
      • classification of an object
    • Class naming conventions -
      • class name must begin with a letter followed by letter, digits, and underscores
      • convention, class names start w/ a capital letter
        • you cannot use. java reserved word to name a variable or class (ie. null)
      • Whitespace is irrelevant to the Java compiler

  • Encapsulation

    • combining data (variables) behaviors (methods) into one package from the users of the object
    • Classes encapsulate several data-fields and behaviors into a single entity
    • Encapsulation combine class-members (methods and variables) in a single scope
      • see video for example

  • Instance-fields

    • an instance-filed, or instance-variable are representative of the properties or attrubutes of a CLASS
    • Value of the field is the Instance-State

  • Instance Methods

    • behaviors of an object are made available to users via obj methods
    • Keep your method clean to make it easier to identify (i.e. method speak = nameSpeak)

  • Access Modifiers:

    • Public - method can be called from any class
    • Private - can only be called from within the same class
    • Protected - method can only be called from classes in the same package or subclasses
    • default (Package private) - method can only be alled from classess in the same package (achieved when ommited public/private/protected)

  • Optional Specifiers

    • static: used for class methods: System.out.println(...)
    • abstract: used when not providing a method body
    • final: used when a method is not allowed to be overrideen by a subclass
    • synchronized: used in concurrency

  • Method Declaration: Method Name - how we identify and call method at hand

    • reserved word or numbers, $, _ string

  • Parameter List: Method does not need to contain parameters

    • Variables should be seperated via commas not semicolon

  • Method Declaration: Optional exception list

  • Method Declaration: Method Body - "concrete body" - method w/ a body not abstract

  • Varargs: Method may use a vararg parameter (variable argu- ment) as if ti was an array. - ** only have one vararg parmeter per method

  • Instance-Variables (Fields)

    • accessors (getters)
    • mutators (Setters)

  • Static Methods and Fields

    • static method does not require an instance of a class - do not have to create an instance of. class to call it
    • means they belong to the class not the instance
    • for utility or helper methods that don't require any object state
    • for state that is share by all insances of a class like a counter (i.e. turtle counter)

  • An instance method can call a static method but a static method cannot call an instance method

  • Static Variables

    • Constants are static variables that meeant to never change during the program - "final" the value it holds is the final thing it can hold
      • variable is the cup holder - super glue is the "final" thats = thats the last cup itll hold, but the state of the cup can be modified

** follow-up via video recording

  • Setters = using void to set the class