Introducing Objects and stuff

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Introducing Objects and stuff

• GABY and MATT

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Definition

• Object a class that is the root of the
  hierarchy tree for all classes in JAVA.
• An object is defined by a class or
• Primitive Data Includes common values such as
  numbers and characters.
• Data Type Defines a set of values and
  operations.
• Operators A symbol that represents an operation
  in a programming language, such as the addition
  operator

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Continued

• Encapsulation the characteristic of an object
  that limits access to its variables and methods.
  All interaction with the object occurs through an
  interface.
• Inheritance The ability to create a new class
  from an existing one. Inherited variables and
  methods of the original class are available in
  the new class if they were declared locally.

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Section 2.1 Using Objects

• Kevin Curtis
• Dennis Truong
• Period 2

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The Basics

• Objects
• The basic software part in an object-orientated
  program.
• Represents output device or file (i.e. monitor)

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The Basics

• For example
• System.out.println (Whatever you are, be a good
  one.)
• System.out represents the output device or
  file
• The objects name is out and stored in the
  system
• class
• The println method will print a string of
  characters to
• the screen.
• The parameter is the piece of data sent to a
  method, or in this example, the string of
  characters printed to the screen.

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Methods and Objects

• Receives information from the parameter
• System.out.println (test)
• Determines how the object functions for example
• print method prints information and stays on the
  same line.
• println method prints information and then skips
  to the next line.

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Methods and Objects
Countdown
System.out
println
main
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Abstraction

• An abstraction means that the details of how it
  works does not matter to the user. An object is
  an example of an abstraction.
• An abstraction hides or ignores certain details.
  With a good abstraction hiding the right details
  at the right time to manage the complexity.
• Level of abstraction the amount of abstraction
  that is used to hide the details

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2.6 Creating Objects
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Introduction

• Variable can hold primitive value or reference
  to object
• The new operator returns a reference to a newly
  created object
• Creating object with new operator is called
  instantiation
• ex. String name new String (Mr.
  Jacobson)
• An object is called instance of particular class
• After the new operator creates the object, a
  constructor is a string literal

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Dot Operator

• When object is instantiated, we use the dot
  operator to get is methods
• Dot operator is added right after object
  reference and is followed by method being invoked
  
• ex. Count name.length()

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The String Class

• String in Java are object represented by the
  string class
• the type shown in front of method name is called
  return type of the method
• A return type void means that the method doesnt
  return a value
• Object immutable when value cant lengthened or
  short nor can any of its character change
• Index is a characters position in string
• The first character is zero

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Wrapper Class

• All primitive type in Java have wrapper class--
  let you create objects representing primitive
  data
• Integer class represent int and double class
  represent a double
• ex. Integer number new Integer (45)
• The Integer and Double objects are immutable
  

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Chapter 4.0 Writing Classes

• By Dina Deng
• April Ochoa

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Objects Revisited

• Example of an ObjectA ball has diameter, color
  and elasticity.
• The properties that describe an object are called
  attributes - defined as the objects state of
  being.
• Behaviors What it does-ex. the ball can be
  thrown, bounced, or rolled.

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• Each object has a state and a set of behaviors.
  The values of an objects variables define its
  state and the methods define its behaviors.
• The action of an object will remain the same, but
  it depends on the objects state.
• The class of an object may contain a method to
  add a new course.
• Software objects can often represent physical
  things, but they dont have to. For example an
  error message can be an object, with its state
  being the text of the message and behaviors,
  including printing the error message. Theres no
  limit for possibilities to just be physical
  things.

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Classes

• An object is defined by a class
• A class can be described as a model, patter, or
  blueprint of the object thats being created. It
  has no memory space for data. Each object has
  its own data space, thus its own state.
• Blueprint - defines the important
  characteristics. Ex. A houses walls, windows,
  doors, electrical outlets, and so on.

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Chapter 4.1 Review

• Anatomy of a Class
• Darwin Arayata
• Stephen Le
• Jibram Martinez

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• Members of the class are classes containing the
  declarations if the data that will be stored in
  each instantiated object and the declarations of
  the methods that can be invoked using an object.
• Refer to the picture on pg. 193 listing 4.1

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Instance Data

• In the coin class, the constants HEADS and TAILS,
  and the variable face are declared inside the
  class, but not inside any methods.
• Location at which variable declared defines its
  scope
• The coin object, for example, has its own face
  variable with its own data space.
  -Reference to Page 197 listing 4.3

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Instance Data continued..

• Attributes such as the variable face are also
  called instance data because memory space is
  created for each instance of the class that is
  created.
• Java automatically initializes any variable
  declared at the class level.

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Encapsulations and Visibility Modifiers

• We can think about an object in one of two ways,
  depending on what we are trying to do.
• First when we are designing and implementing
  objects
• We have to define the variables that will be
  held in the object and write the methods that
  make the object useful
• Objects should be encapsulations lated. The rest
  of a program should work with an object only
  through a well defined interface

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Encapsulations and Visibility modifiers
continued.

• When we are designing a solution we have to think
  about the objects in the program work with each
  other
• In java we create object encapsulations using
  Modifiers
• A modifier is a java reserved word that names
  special characteristics of a programming language

25
Continued

• Some Java Modifiers are called visibility
  modifiers
• They control whether client code can see whats
  inside an object

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Anatomy Of A Method

• By Jei Mercado, David Chap, and Kevin Lai

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Anatomy Of a Method

• A method declaration defines the code that is
  executed when the method is invoked.
• When it is done, control return to the location
  where the call was made and execution continue.
• Define the same class
• Define Programs

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Return Statement

• A return value must match the return type in the
  method header.
• Return type in the method header can be a
  primitive type class name Reserved word void
• Void is used as a return type
• Return is double

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Parameter

• Pass through when invoked
• List in the header of this method list the type
  of value that are passed their name
• Formal parameter
• Actual value pass into actual parameter

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Constructor

• Cannot have any Return type even void
• Is the same name as the class
• Each class have a different structure

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Local Data

• A variable declared in a method is local to that
  method and cannot be used outside of it
• Instruct data

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Lesson 4.3

• Method Overloading

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Uses

• Performing similar operations on different types
  of data.
• Using the same method name with different
  parameter lists for several different methods.

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What is needed

• The compiler still needs to match up each
  invocation with a specific method declaration.
• It needs a signature, which is the methods
  name, number, type, and order of its parameters.

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What happens

• First, the value in the variable is converted to
  a string representation.
• Next, the two strings are concatenated into one
  longer string.
• Last, the definition of println that accepts a
  single string is called.

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Public class SnakeEyes public static void
main (String args) final
int ROLLS 500 int snakeEyes 0,
num1, num2 Die die1 new Die()
Die die2 new Die(20) for
(int roll 1 roll lt ROLLS roll)
num1 die1.roll()
num2 die2.roll()
if (num1 1 num2 1)
snakeEyes
System.out.println (Number of rolls
ROLLS) System.out.println (Number
of snake eyes snakeEyes)
System.out.println (Ratio
(double)snakeEyes/ROLLS)
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Output

• Number or rolls 500
• Number of snake eyes 6
• Ratio 0.012

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Chapter 4 - Section 4our

• Method Decomposition

By Miguel, Marvin, and Eric
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What is method decomposition????
-a complicated method can be broken into several
simpler methods and helped by support methods.
-in an object-oriented design, breaking up
methods must happen after objects have been
broken.
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For example
-PigLatinTranslator.java (pg. 216-218)
-the translate method is broken up into simpler
methods and uses several support methods.
-translateWord is a support method.
-beginsWithVowel, beginsWithBlend, startsWith are
simpler methods that help the translate method do
its job.
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THE END
Or is it?
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Object Relationship

• By
• Dustin and Greg

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Association

• Use Relationship- when two classes are aware of
  each other and may use each other.
• Ex. An artist object draws a picture object

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Association of objectsof the same class

• A method invoked through one object may take as a
  parameter another object of the same class

Woman object taking parameters from Man object
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Aggregation

• An aggregate object is made up, in part, of other
  objects, forming a has-a relationship
• Ex. A car has a tire

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Great Job!

• I will send a copy to each computer
• This is a good summary of some of the object
  oriented programming ideas