Special Topics: Java

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Special TopicsJava

• Introduction

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Goal

• My goal is to familiarize you with the Java
  platform and some of its capabilities.
• The successful student will be able use the
  standard features and at least a portion of the
  Enterprise Edition features
• We will also use the course as a vehicle to talk
  about Object Oriented Programming as well as
  Extreme Programming as well.

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The Course

• Assumes familiarity with C/C or a similar high
  level programming language
• Will move quickly and not dwell too much on
  syntax
• Will have different requirements for Graduates
  and Undergraduates
• Will involve both individual and paired projects.

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The Texts

• Head First Java
• Not your usual text
• Does a good job of presenting concepts
• Somewhat interesting to read
• Main shortcoming is that it isnt a reference
  book (Will use the net as a reference)
• Java 2 Enterprise Edition in a Nutshell
• A quick reference on Enterprise Edition topics
• Will get into that as we go through the course

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• Grading
• Midterm (20)
• Projects (50)
• Paper (5)
• Final (25)

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Mode of This Class

• This is a Distance Learning Class. That means
  that it is being presented through a computer
  connection to a different site.
• Use the mikes when asking questions so the
  other site can hear you!
• The overheads will be on the web.
• Will not always originate from Toledo I expect
  to hold some of the classes at the other site.
  Not quite sure how and when this will occur yet.

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Graduate Students

• Graduate Students will have separate, more
  challenging projects (except for the first
  project).

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Web Sites

• We have 3 places that we can go for web sites
• http//mars.eecs.utoledo.edu/java
• http//chee1.ni.utoledo.edu/sip
• http//www.dl.utoledo.edu/login.htm

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Other Resources

• http//java.sun.com/ -- Sun developers connection
• http//www.safari.com/ -- online bookshelf
• http//www.eclipse.org/ -- the eclipse
  development environment

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Online Contact

• There is a Chat Room set up under DL
• I will have some set times Im available online
  especially for distance learning students.
• There will be a course bulletin board available
  as well.

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The Compilation Process
Type in Source(.java)
Compile javac filename.java
Compiler
Byte Codes(.class)
Run java filename
JVM
CPU
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Java Versions
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A First Program

• public class FirstProgram public static void
  main (String arguments) System.out.println(Th
  is is a test) System.out.println(It is only
  a test)
• System.exit(0)
• Points
• Public means something is accessible by
  everybody. If the class itself was NOT public it
  wouldnt be accessible outside of the file.
• When you run a java application the class that
  the program starts in must have a main method.
• System.out is about the same as cout or stdout.

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Statements

• Assignments
• Follow normal rules for precedence
• () Parenthesis (grouping)
• , /, Multiplication, division, remainder
• , - Addition and Subtraction

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More Statements

• Loops
• while ( condition )
• do . while ( condition)

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More Loops

• for (init condition incr) .

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Conditions

• Conditions are Identical to C/C
• lt Less Than
• gt Greater Than
• lt Less Than or Equal to
• gt Greater Than or Equal to! Not equal
• Equal
• And
• Or
• ! Not

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Conditional Statements

• If-Else
• if (condition)
• true part
• else false part

• Switch
• switch ( expression) case value1
• breakcase value2
• break
• default
• break

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Declarations and Types

• Declarations
• type variable1, variable2,
• Variable Naming Rules
• Must begin with a letter, , or underscore
• Must consist only of Letters, , underscores,
  and digits
• Cannot be a reserved word.

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Primitive Types

• All Primitive Types start with a lower case
  letter
• boolean true or false
• char can hold a unicode character
• byte -128..127
• short -32768..32767
• int -2147483468..2147483467
• long 64 bits (you do the math!)
• float 32 bits
• double 64 bits
• Remember Be Careful! Bears Shouldnt Ingest
  Large Fluffy Dogs

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Objects

• What I dont want you to do is write programs
  exactly like you have done in C and (sometimes)
  in C.
• Java was designed to be based on objects
• This should encourage you to look at your designs
  in a different way

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Simplistic View

• Define the important pieces
• Decide on the objects in your system (tend to be
  nouns)
• What does each object know? (instance variables
  or attributes)
• What does each object do? (methods)

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Class ! Object

• Classes arent objects!
• Class is a blueprint or description of an object.
  
• The object is the actual instance. It is
  constructed using the Class as the guide.
• Head First Java builds a dog class and we will
  build one too. Ours will differ slightly.

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Define The Class Using UML

• UML Unified Modeling Language
• Basics Class Diagrams
• Relationships are indicated with connectors
• Unidirectional association
• Bidirectional association
• Dependency
• Generalization (inheritance)

Class Name
Instance Variables
Methods
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Building Our Class From Our UML Diagram

• public class Dog
• string breed, nameint weight, height
• void bark () System.out.println( Woof!
  Woof!)
• void scratch()
• void beg()
• void rollover()
• void sit()

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Still Need a Main Program

• Main program can be in a separate class in this
  case we will do it that way.
• Remember file name should match class name!

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The testing class

• public class TestDog
• public static void main(String arguments)
  Dog fido new Dog()
• fido.name Fido
• fido.breed Mixed
• fido.height 45 fido.weight 170
• fido.bark()
• fido.rollover()
• System.exit(0)

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Objects are Manipulated via References

• Dog fido new Dog()
• Dog bingo
• Fido is a reference to the object -- not the
  actual object!
• bingo fido // assigns the reference
  does // NOT create a new object!

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Arrays are Objects Too!

• We havent mentioned arrays but they tend to be
  objects as well.
• Declaration
• int values// Creates a reference to an array
• values new int 20 // Creates the array and
  // connects it with values.
• values0 123 // Using the array...
• values1 -25

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Garbage Collection

• Rather than making the programmer delete objects
  once they are no longer in use Java does it for
  you.
• The process is known as garbage collection.

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How does it know what to collect?

• Objects have a reference count.
• The reference count determines how many
  references to the object exist.
• If there are no references to an object it is
  marked for garbage collection since there is no
  way anybody can ever use it again.

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Programming Environments

• The JDK Java Developers Kit from Sun.
• Free
• Command Line based
• Need your own editor
• Eclipse
• Open Software IDE
• Not Just Java (but originally so it still does a
  good job)
• Extendable Framework
• Sun Workshop
• IDE
• NetBeans Based

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Projects for This Class

• Will be tested on Multiple Platforms
• Will be implemented with documentation
• UML diagrams
• JavaDoc Comments
• Will encourage you to use a code control system.

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Sample Program Hit List
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The Artist Class

• /
• _at_author Jerry Heuring
• Created Dec 31, 2003
• _at_version 0.0
• Bugs
• Revisions
• The artist in this case is represented with
  their first
• and last names along with a birth and death
  date.
• Date is a class inside of Java and the import
• java.util. imports all the types in a group.
  We could
• alternately do a import java.util.Date to just
  import
• the one class.

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• Comments starting with the / are javadoc
  comments and can be converted into
  documentation using a tool. We will talk about
  the details as we pick up more stuff in the
  class. /
• import java.util.
• public class Artist
• private String firstName, lastName
• private Date born, died

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Default Constructor

• / Artist() -- Default constructor. No
  name, no dates/
• public Artist() born null died
  null firstName "" lastName ""

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The Complete Constructor

• / Artist -- The complete constructor. User
  provides dates and names. If the artist
  is still living pass null for the date
  they died. _at_param first The artist's first
  name _at_param last The artist's last name
  _at_param b The birth date of the artist _at_param
  d The death date of the artist (may be null) /
• public Artist(String first, String last, Date b,
  Date d) born b died d firstName
  first lastName last

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getName and getFirstName

• / getName() - returns the full name of the
  artist _at_return the full name of the
  artist /public String getName() return
  firstName " " lastName/
  getFirstName() -- get the artist's first name
  _at_return the first name of this artist
  /public String getFirstName() return
  firstName

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getLastName()

• / getLastName() -- get the artist's last
  name _at_return get this artist's last name
  /public String getLastName() return
  lastName

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getLastName isDead

• / getLastName() -- get the artist's last
  name _at_return get this artist's last name
  /public String getLastName() return
  lastName/ isDead -- returns a true if
  the artist is deceased _at_return true if the
  artist died prior to the current
  date. false otherwise. /public boolean
  isDead() if (died ! null) if ((new
  Date()).after(died)) return
  true return false

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Died and Main

• / died -- set the date the artist died.
  _at_param dod the date of death for the artist.
  /public void died(Date dod) died
  dod/ I don't have anything in the main
  program right now. Normally my main routines
  contain at least some minimal test code. We
  will add tests as we go on... _at_param
  args The command line arguments
  nothing recognized right now. /public static
  void main(String args)

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Album

• / _at_author Jerry Heuring Created Dec 31,
  2003 Description This class
  represents an album. Each album has an
  artist associated with it and it has a number of
  tracks (currently artificially limited to
  100 tracks). The current version has a
  pair of constructors but probably needs yet
  another constructor that will accept tracks
  as well. _at_version 0.0 Bugs
  Revisions /

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Default constructor

• public class Album private int inUseprivate
  Track tracks new Track100private String
  titleprivate Artist artist/ A pair of
  constructors -- one with no arguments and one
  with a title and an artist. Tracks must be
  added later using the addTracks method.
  /public Album() inUse 0 title
  "" artist null

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Album(), getTitle(), getArtist()

• public Album(String t, Artist a) title
  t artist a inUse 0/ getTitle --
  return the album's title _at_return the album's
  title /public String getTitle() return
  title/ getArtist -- return the artist
  who recorded the album Note There should be
  a way to have more than one artist on an
  album but I'm not going to address that
  here. _at_return the artist's name /public
  Artist getArtist() return artist

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getRunningTime()

• / getRunningTime sums the running times of
  the separate tracksand returns a time, in
  minutes, for the total album. _at_return the
  total running time of the album in
  minutes /public float getRunningTime()
  float totalTime 0.0f int
  currentTrack for ( currentTrack0
  currentTrackltinUse currentTrack)
• totalTime trackscurrentTrack.getLength()
  return totalTime

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getNumberOfTracks(), addTrack()

• / getNumberOfTracks _at_return the
  number of tracks currently on the album
  /public int getNumberOfTracks() return
  inUse/ addTrack -- Add a track to an
  album _at_param newTrack the new track to be
  added to the album /public
  void addTrack(Track newTrack) if (inUse lt 100)
  tracksinUsenewTrack inUse

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Play

• / play -- plays all the tracks on the album.
  The racks are played in the order they were
  added to the album. It might be interesting
  to allow other ways to play the tracks.
  /public void play() int trackNbr for
  (trackNbr 0 trackNbr lt inUse
  trackNbr) trackstrackNbr.play() publ
  ic static void main(String args)

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Track Class

• / _at_author Jerry Heuring Created Dec 31,
  2003 Description This class
  represents a track on a particular album. It
  currently has no way of distinguishing the
  type of data but an array of bytes is currently
  being used to represent the audio data.
  _at_version 0.0 Bugs Revisions
  /

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• public class Track String titlefloat
  runningTimebyte audioAlbum album

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Track() constructors

• / The default constructor -- no title, no
  audio, no album. /public Track() title
  "" runningTime 0.0f album null/
  A complete constructor for a track _at_param
  t the title of the track _at_param a the album
  the track is associated with _at_param time the
  running time of the track _at_param song the byte
  array of data for playing the
  album /public Track (String t, Album a, float
  time, byte song) title t album
  a runningTime time audio
  song

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getTitle(), getAlbum()

• / getTitle -- get the title for this track
  _at_return title for track /public String
  getTitle() return title/ getAlbum --
  get the album that the track appears on
  _at_return the album the track appears on.
  /public Album getAlbum() return album

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getArtist(), hasAudio()

• / getArtist -- get the artist associated
  with the track. _at_return
  the Artist object associated with the track
  /public Artist getArtist() return
  album.getArtist()/ hasAudio -- returns
  true if the byte array exists for
  this track. _at_return -- true if byte array
  exists, false otherwise /public boolean
  hasAudio() return audio ! null

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Play()

• / play -- plays the audio track if it
  exists. Lots of stuff still to be done
  here. Haven't settled on a format or a method
  to actually play it. Will we need to hold the
  entire track in memory or allow a file
  reference? /
• public void play () if (audio ! null)
• // Need to do something to play the
  music....

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getLength()

• / getLength -- return the running time
  in minutes for this track
  _at_return the running time of the track /public
  float getLength() return runningTimepublic
  static void main(String args)

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Hints and Gotchas

• The classes must be in files named the same as
  the class (Case Matters)
• Artist.java
• Track.java
• Album.java
• When you compile (if you use javac) the compile
  command has the full name
• javac Artist.java Track.java Album.java

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Hints and Gotchas Continued

• The output will be .class files if it is
  successful.
• To run using a command line
• java classToStartIn
• There is no .class after the class name in the
  command to run. It is simply the class name.
• java Album

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Where Can I Get The Software?

• Eclipse http//www.eclipse.org/
• JDK http//www.javasoft.com/
• Java http//www.sun.com/
• Sun One Studio
• Ill also make a few CDs available to keep the
  net a bit less loaded.

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Project 1

• Description
• You are to implement a login system for a
  company. Users log in with a username and a
  password. The system needs to keep track of the
  last login time for a particular user as well as
  group membership for the user (the user may be a
  manager, clerical, consultant, etc). Groups may
  be extended further in the future to include
  detailed permissions for objects controlled by
  the system.

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Project 1 -- Input

• Your program should allow the user to input a set
  of groups for the system followed by a set of
  users. The user information must include the
  users first and last names as well as the
  username and password. It should also allow for
  input of a set of groups for the user.
• The application should also implement an object
  that will be responsible for encrypting the
  passwords. The passwords for the users should be
  stored in encrypted form. When a user attempts
  to log in the password they type in should be
  similarly encrypted and then compared to the
  stored password. The company has not settled on
  an encryption method so that you should provide a
  class that has the routines for encrypting the
  password but does not actually encrypt the
  password.

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Project 1 -- Output

• Your program should allow the testing team to
  login to user accounts and, if the login is
  successful, it should print out the information
  associated with the user account (except for the
  password!). It should also allow the testing
  team to dump all information (including the
  passwords) to the screen.

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Deliverables

• Turn In
• A listing of your code.
• E-Mail to jheuring_at_eecs.utoledo.edu
• Your source files (.java).

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Grading

• Correctness
• Does the program do what it is supposed to?
• Does it handle extreme cases correctly?
• Coding Style (Programming Practices)
• Implies indentation, readability, good choice of
  algorithms, good naming practices, reasonable
  design.
• Deliverables
• Did you give me what I asked for?
• Can I identify it as yours?
• Does it compile?