An Introduction to Java and Program Design

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Chapter 1

• An Introduction to Java and Program Design

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Introduction

• A program is a step-by-step series of
  instructions for a computer
• Computer programming is the process of writing
  these instructions
• Programmers, or developers, design and write
  programs using a programming language or
  development tool
• Java is a programming language that provides the
  structure for efficient and economical programs

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What Is Java?

• High-level language
• Object-oriented
• Data and operations are packaged into a single
  unit called an object
• Basic syntax derived from C, C, and Smalltalk
• Designed by a team from Sun Microsystems led by
  James Gosling in the early 1990s

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What Is Java?

• Parsimonious
• Compatible with older versions
• Robust
• Strongly typed and incorruptible data
• Secure
• Protection against misuse of code
• Portable
• Platform-independent

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Java Program Types

• Console and Windowed applications
• Applets
• Servlets
• Web Services
• JavaBeans

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Console Applications

• Stand-alone programs using a command-line
  interface

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Windowed Applications

• Stand-alone programs using a graphical user
  interface (GUI)

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Applets

• Client-side programs executed as part of a
  displayed Web page

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Servlets

• Server-side programs hosted and run on a Web
  server
• Used in conjunction with Java Server Pages (JSP)
  to provide sophisticated server-side logic
• Enable connections to server databases through
  Java Database Connectivity (JDBC)

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Servlets

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Web Services

• Services receive information requests over the
  Web and return the requested data

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JavaBeans

• Reusable software components

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Programming a Computer

• Companies need developers to build general
  application software packages
• Custom applications are built for specific needs
• Existing programs need maintenance, monitoring,
  and upgrades
• New applications will be needed due to emerging
  technologies

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Program Development Cycle

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Phase 1 Analyze the Requirements

• Verify that the requirements are clear and
  complete
• Evaluate the problem to determine that it is
  solvable using a program
• List the required input and output data
• Determine whether the input data is available for
  testing

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Phase 1 Analyze the Requirements

• Ensure that a solution, or algorithm, can be
  developed with the information provided in the
  requirements
• Verify the user interface specifications

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Phase 2 Design the Solution

• Develop a logical model that illustrates the
  sequence of steps you will take to solve the
  problem
• Use design tools such as storyboards, class
  diagrams, flowcharts, and pseudocode to outline
  the logic of the program

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Phase 2 Design the Solution

• Storyboards are sketches of the user interface

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Phase 2 Design the Solution

• Class Diagrams illustrate the attributes and
  methods of a class of objects
• Attributes define the characteristics of a class
• Methods are instructions a class uses to
  manipulate values, generate outputs, or perform
  actions

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Phase 2 Design the Solution
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Phase 2 Design the Solution

• Flowcharts graphically represent the logic used
  to develop an algorithm
• Control structures allow the programmer to
  specify the code that will execute only if a
  condition is met
• Flowcharts use pseudocode, English, or
  mathematical notation inside symbols to represent
  the steps of a solution

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Phase 2 Design the Solution

• Pseudocode is an English representation of how
  the program code should be written

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Phase 3 Validate the Design

• The programmer steps through the solution with
  test data
• The user agrees that the program design solves
  the problem put forth in the requirements
• The user verifies that the initial requirements
  document contains all necessary requirements

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Phase 4 Implement the Design

• Write the code that translates the design into a
  program
• Create the user interface
• Create comments within the code that explains the
  purpose of the code
• Unit testing
• Test the code as it is written
• Test related code

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Phase 4 Implement the Design

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Phase 5 Test the Solution

• Create a test plan with test cases of sample
  input data and expected output
• Perform integration testing to ensure that
  components interact correctly
• Test boundary values
• Document any problems
• If results are unsatisfactory, a new iteration of
  the development cycle begins

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Phase 6 Document the Solution

• Requirements documents, program design documents,
  user interface documents, and documentation of
  the code
• Test cases and proof of successful completion of
  testing
• Program code should be archived electronically

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Object-Oriented Programming and Design

• Object-oriented programming
• Data and the code that operates on the data are
  packaged into a single unit called an object
• Object-oriented design
• Identifies how objects interact with each other
  to solve a problem

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Object-Speak

• Aggregation
• The concept of an object composed of another
  object
• Generalization hierarchy
• A tool displaying a hierarchy of classes,
  including superclasses and subclasses
• Instance
• A specific use of a class

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Object-Speak

• Operation
• Activity that reads or manipulates the data of an
  object
• Message
• Activates the code to perform one of the
  operations
• Trigger
• Causes the message to be sent
• Event
• The process of a trigger sending a message that
  results in an operation

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Object-Speak

• An event diagram graphically represents
  relationships among event and operations
• Useful for designing event-driven programs
• Part of the Unified Modeling Language (UML)
• The UML provides a standardized model to describe
  object-oriented designs graphically
• The UML is a system of symbols to represent
  object behavior and program behavior

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Encapsulation

• The process of hiding the implementation details
  of an object from its user
• The user is shielded from the systems complexity
• Information hiding provides access to an object
  only through its messages
• Objects can be modified without requiring
  application modification

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Inheritance

• An efficient way to reuse code by defining a
  subclass as an extension of another class
• The subclass inherits all the data and functions
  of the superclass
• The subclass has at least one attribute or method
  that differs from its superclass

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Polymorphism

• Allows an instruction to be given to an object
  using a generalized command
• The same command will obtain different results
  depending on the object receiving the command
• The specific actions internal to the object are
  encapsulated from the user

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Rapid Application Development

• Pre-built objects speed up program development

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What Is the Java SDK?

• The Java Software Development Kit (SDK) is a
  programming package to develop Java applications
• The Java Runtime Environment (JRE) provides the
  tools to deploy Java applications

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Features of the J2SE

• The Java Compiler
• Converts code into bytecode
• The Java Virtual Machine
• Contains an interpreter to execute the bytecode
• The Java API
• The standard set of packages available in Java
• The Java Applet Viewer
• Mini browser to display Java applets

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Other Java Development Tools

• VATE (value-added text editor)
• Color codes elements and numbers lines
• Examples TextPad, JCreator, JGrasp
• IDE (integrated development environment)
• Builder tool to aid coding and debugging
• Examples Sun ONE Studio, JBuilder, Visual Age,
  Simplicity
• Web server
• Deploys servlets
• Example Tomcat

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Chapter 1 Homework

• Short Answer, pages 35 36
• 1, 2, 5 10
• Only type the answers, not the questions
• Programming Assignments
• Pages 38 43
• 1, 2, 4, 10
• All answers must be typed and printed out.
• Due 9/13/07