Java for ColdFusion Programmers

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Java for ColdFusion Programmers

• Hal Helms
• halhelms.com

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What we'll cover

• Why OO?
• What is OO?
• Why Java?

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Theory of Constraints

• According to the Theory of Constraints, any
  system has only one current constraint that
  hinders the system from producing
• Working on anything other than that is
  misdirected effort and can actually be worse than
  doing nothing

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What's so great about OO?

• The greatest threat to softwareto both
  successful deployment and maintenanceis
  complexity
• Object orientation offers us the best tools yet
  devised for managing that complexity

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Food for thought

• "Any intelligent fool can make things bigger and
  more complex. It takes a touch of geniusand a
  lot of courageto move in the opposite
  direction."
• -Einstein

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What tools are available in OO for managing
complexity?

• Encapsulation
• Polymorphism
• Inheritance

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Fabulous prizes time

• List as many data types as you can

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About data types

• The primary goal of a type system is to ensure
  language safety by ruling out all untrapped
  errors in all program runs. The declared goal
  of a type system is usually to ensure good
  behavior of all programs, by distinguishing
  between well typed and ill typed
  programs. Cardelli

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What is object orientation?

• Object orientation (OO) is a way of constructing
  software such that an simplified, idealized model
  of the world under consideration is created in
  software components that encapsulate the
  statefulness and behavior of the inventory of the
  world and that may change their state or perform
  some behavior in response to a message sent to
  them

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What did he just say?

• "simplified, idealized model of the world under
  consideration is created in software components
  that encapsulate the statefulness and behavior "

PackageDeliverer
route Route assignedTruck Truck hourlyPayrate
numeric hoursWorked numeric
deliverPackages()boolean collectCOD()
void completeTimecard() void getPayDue() numeric
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What did he just say?

• that may change their state or perform some
  behavior in response to a message sent to them

doC()
doB()
route assignedTruck hourlyPayrate hoursWorked
obj.getRoute()
getRoute()
doD()
obj.hoursWorked
doH()
doE()
doG()
doF()
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Breathing life into models

• Defining classes is done at design time
• At run time, classes are instantiated, producing
  objects
• An OO application is nothing but a number of
  objects sending messages back and forth to on
  another

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What's so great about Java?

• The power of Java lies in object orientation
• For most procedural programmers, OO takes time to
  penetrate
• When learning OO, it's very important to lay good
  foundations
• Java is simply a very good implementation of
  object orientation

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Java Encapsulation

• Data and behavior in a single software component
  the class
• A class is like a blueprint or cookie cutter from
  which objects are created

Class
Objects
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Encapsulation

• Encapsulation allows the details of a component
  to be hidden from users of the component. In
  place of exposing its internals, a
  well-encapsulated component exposes an interface
  or specification.

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A specification

• The Cat class has, as part of its specification,
  a play() method. When called, each Cat object
  will carry out its play method. We know only what
  it will do, not how it will do it.

I can play()
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Encapsulation in Java

• Let's build a simple class, Cat
• The Cat class will have
• properties
• name
• color
• methods
• get/setName()
• get/setColor()
• play()
• Remember that Cat is a blueprint. To create an
  actual Cat object, we'll use CatDemo.java

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Polymorphism

• Polymorphism allows different objects to be
  treated as having the same specification and/or
  one object to be treated as belonging to
  different specifications

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Treating different objects as having the same
specification

• Java allows different objects to assume the same
  type
• Java allows the same object to assume different
  types

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Polymorphism in Java

• Let's build a simple class, RobotDog
• The RobotDog class will have
• properties
• voltage
• batteryLife
• methods
• get/setVoltage()
• get/setBatteryLife()
• play()

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Interface

• A specification without implementation
• Acts as a data type
• An interface is like a role that an object can
  step into
• The object, joe, might be "born" as a Welder, but
  may also implement
• Father
• Son
• Voter
• PokerPlayer

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Inheritance

• A special case of polymorphism in which one class
  is a specialized type of another class
• HourlyEmployee Employee
• SportsCar Car
• TypicalManager CluelessDolt
• When one class inherits from another, it inherits
  all those properties and methods not declared to
  be private

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Why is OO a big deal?

• If you're a programmer, you must know OO
• OO gives you, the programmer, better tools for
  dealing with
• changing requirements on current projects
• maintaining existing code
• team development

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But why Java?

• So that you'll learn OO right
• Once you learn OO, you can then use
• CFCs
• C.NET
• Visual Basic.NET
• Ruby
• Eiffel
• etc.

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Food for thought

• "Students usually demand to be taught the
  language that they are most likely to use in the
  world outside. This is a mistake. A well taught
  student can easily pick up the languages of the
  world, and will be in a far better position to
  recognize their bad features as they encounter
  them."
• C. H. Lindsey

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To learn more

• Books
• Head First Java published by O'Reilly
• Java for ColdFusion Developers by Eben Hewitt
• Training/Mentoring
• Java for ColdFusion Programmers (halhelms.com)