OOP

1
OOP JAVA
2
HelloWorld.java

• / The HelloWorld class is an application that
  displays "Hello World!" to the standard output.
  /
• public class HelloWorld
• // Display "Hello World!"
• public static void main(String args)
  System.out.println("Hello World!")
• Compile C\gt javac HelloWorld.java
• Create java bytecode HelloWorld.class
• Run C\gt java HelloWorld

3
HelloWorld.java (Applet)

• webpage.html
• HelloWorldApplet.java

4
Definitions of OOP

•  Class
• A class defines the abstract characteristics of a
  thing (object), including the thing's
  characteristics (its attributes or properties)
  and the things it can do (its behaviors or
  methods or features).
• For example, the class Dog would consist of
  traits shared by all dogs, for example breed, fur
  color, and the ability to bark.

5
Definitions of OOP

• Object
• The class of Dog defines all possible dogs by
  listing the characteristics that they can have
  the object Lassie is one particular dog, with
  particular versions of the characteristics. A Dog
  has fur Lassie has brown-and-white fur.
• In programmer jargon, the object Lassie is an
  instance of the Dog class. The set of values of
  the attributes of a particular object is called
  its state.

6
Definitions of OOP

• Method
• An object's abilities. Lassie, being a Dog, has
  the ability to bark. So bark() is one of Lassie's
  methods. She may have other methods as well, for
  example sit() or eat(). Within the program, using
  a method should only affect one particular
  object all Dogs can bark, but you need one
  particular dog to do the barking.

7
Definitions of OOP

• Message passing
• "The process by which an object sends data to
  another object or asks the other object to invoke
  a method."

8
Definitions of OOP

• Inheritance

9
Definitions of OOP

• Encapsulation 
• Conceals the exact details of how a particular
  class works from objects that use its code or
  send messages to it. So, for example, the Dog
  class has a bark() method. The code for the
  bark() method defines exactly how a bark happens
  (e.g., by inhale() and then exhale(), at a
  particular pitch and volume).

10
Definitions of OOP

• Polymorphism
• is the ability of behavior to vary based on the
  conditions in which the behavior is invoked, that
  is, two or more methods, as well as operators
  (such as , -, , among others) can fit to many
  different conditions.
• Ex. method signatures would be, respectively,
  very similar to add(int a, int b) and add(String
  a, String b). This is an example of Parametric
  Polymorphism. The returned type and used
  modifiers, of course, depend on the programmer
  interests and intentions.

11
JAVA basics

• http//leepoint.net/notes-java/index.html

12
Javas Scope

• Scope is a term used to define where a variable
  is defined.
• EX.
• Function eat()
• int money100
• Print money
• Function buy()
• int money200
• Print money
• main()
• int money0
• eat()
• buy()
• Print money