UMass Lowell Computer Science 91.460 Java and Distributed Computing Prof. Karen Daniels Fall, 2000

1
UMass Lowell Computer Science 91.460 Java and
Distributed Computing Prof. Karen Daniels Fall,
2000

• Lecture 4
• HW1 Electronic Submission of Part 2
• Jini Overview (continued)
• C Diagnostic Results
• Java Fundamentals
• Wed. 9/13/00

2
Electronic Submission of Homework 1, Part 2

• Mon, 9/18 Hello World programming
• (application and applet)

• Note If you want to use Swing on HW1 in UML CS
  UNIX environment, use the Java version located
  in /usr/opt/java122/bin
• /usr/opt/java122/bin/javac
• /usr/opt/java122/bin/java
• Entire class will transition to this Java
  version starting with HW2.

Homework is due at the start of lecture on the
due date.
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Electronic Submission of Homework 1, Part 2

• Mon, 9/18 Hello World programming
• (application and applet)

• To submit your files electronically, use the UNIX
  submit command
• Example for 3 files
• submit kdaniels hw1 filename.java filename.class
  filename.html
• Youll submit 5 files for HW1, part 2 2 for
  application, 3 for applet
• Submission deadline is 930 a.m. on Monday, 18
  September
• I have now set it up to allow multiple
  submissions before the deadline
• Bring a paper printout of your code to give to
  me at start of Mondays lecture

Homework is due at the start of lecture on the
due date.
4
Jini Overview (continued)
5
Requirements for Service, Client

• Participate in discovery to find a Lookup Service
• Communicate with a Lookup Service to receive
  service proxy

To be a Jini Service
To be a Jini Client

• Either you or a delegate must be able to
• Connect to a TCP/IP network ( )
• Participate in discovery to find a Lookup Service
• Register with a Lookup Service to provide proxy
• Keep leases current

Extra machinery needed - http server(s) for
each machine to offer up downloadable code - RMI
activation daemon
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Hello World in a Jini Setting...
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Who Else is in the Game?(other providers of
coordination frameworks/connection
technologies/service architectures for
distributed computing)

• HAVi
• Sony, Sharp, Toshiba, Philips, RCA, Matsushita,
  Hitachi, Grundig
• Microsoft HP
• ChaiAppliance Plug and Play
• eSpeak
• Universal Plug and Play
• Network protocol level
• XML device description
• Salutation Framework

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Further Information Jini

• Sun web sites
• http//www.javasoft.com/jini
• http//www.jini.org
• Development Books
• Core Jini by W. Keith Edwards
• The Jini Specification by Arnold, OSullivan,
  Scheifler, Waldo, and Wollrath
• Gartner Advisory
• Java Jini A Killer-App Enabler for Network
  Computing? http//gartner.jmu.edu/research/ras/830
  00/83044/83044.html

portions of this slide contributed by Ayal Spitz
9
C Diagnostic Results
Number of Students
17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
Number of Correct Responses
Most students ran out of time
1 2 3 4 5 6
7 8 9
Question Number
10
Java Fundamentals

• 1 Java fundamentals
• applets, applications, data types, control
  structures, OO programming, files
• 2 Advanced Java concepts Java support for
  distributed computing
• GUI/events, graphics, exceptions, advanced data
  structures, threads/ multithreading, RMI
• 3 Distributed computing using a sample
  Java-based environment Jini

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Syllabus for Part 1 of the Course
Part 1
Closed book Worth 15 of grade
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Why Java Distributed Computing?

• Platform independence helps with heterogeneous
  hardware, software challenge
• Built-in support for
• Multithreading concurrent multiple activities
• Client-Server computing servlets, JDBC
• Remote Method Invocation (RMI) method calls
  across network
• Networking socket-based communication views
  networking like file I/O

For insight into the original Java vision, see
the original Java whitepaper by James Gosling at
http//java.sun.com/people/jag/OriginalJavaWhitepa
per.pdf
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C to C to Java At a Glance
C
Java
C
Primitive Data Types Arrays Struct, Union,
Enum Preprocessor Directives Operators Expressions
Control Statements Functions Pointers Dynamic
Memory Mgt File I/O Exception Handling
Primitive Data Types Arrays Struct, Union,
Enum Preprocessor Directives Operators Expressions
Control Statements Functions Pointers Dynamic
Memory Mgt File I/O Exception Handling Classes Mul
tiple Inheritance Polymorphism Templates
Primitive Data Types Arrays Operators Expressi
ons Control Statements Dynamic Memory
Mgt File I/O Exception Handling Classes,
Interfaces Inheritance Polymorphism Su
pport for DBs, networks, GUIs, events, graphics,
threads, libraries
u
u
Procedural/OO, Compiled Language
Procedural, Compiled Language
OO, Interpreted Language
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Introduction to Java Applications

• Java application is executed using the Java
  interpreter (but not inside browser like an
  applet)
• Application begins execution in main( )
• main( ) is static method inside class
• no convenient input from command line
• System.exit(0) // required to clean up
• // after
  GUI/graphics

javac Welcome1.java java Welcome1
Welcome1.java
// Save this in file Welcome1.java public class
Welcome1 public static void main( String
args ) System.out.println( "Java is
fun!" )
Welcome1.class
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Introduction to Java Applets

• Java applet is executed inside a WWW browser (or
  appletviewer) using a Java interpreter that is
  inside the browser.

// Save this file in Welcome1Applet.java import
java.applet. import java.awt. public class
Welcome1Applet extends Applet public void
paint(Graphics g) g.drawString( "Java
is fun!, 25, 50 )
javac Welcome1Applet.java appletviewer
Welcome1Applet.html
Welcome1Applet.java
Welcome1Applet.class
Welcome1Applet.html
Save this file in Welcome1Applet.html
ltHTMLgt ltAPPLET codeWelcome1Applet.class
width150 height100gt lt/APPLETgt lt/HTMLgt
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Introduction to Java Applets (continued)

• Order of (a subset of) applet method invocations
• init( )
• start( )
• paint( )

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Java Variables

• Two types
• primitive data type variable (a.k.a. variable)
• always passed by value
• initialized by default to 0 if numeric false if
  boolean
• except for local variables
• value is constant if final keyword is used
• reference variable (a.k.a. reference)
• refers to memory location of object
• always passed by reference
• initialized by default to null

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Java Primitive Data Types
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Java Array Class

• Declarations
• One-dimensional
• int c c new int 8
• int c new int 8
• final int ARRAY_SIZE 8 int c new int
  ARRAY_SIZE
• int c 32, 44, 6, 7, -1, 25, 88, -31
• Multi-dimensional (e.g. 2)
• int c 32, 44, 6, 7 , -1, 25, 88,
  -31
• int c new int24
• int c new int2 // allocate rows
  for non-rectangular array
• c0 new int3 // allocate columns for
  row 0
• c1 new int4 // allocate columns for
  row 1
• Knows its own length! (e.g. c.length)
• Bounds are checked for you!

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Java String Class (basics)

• String is a series of characters treated as a
  single unit
• Declarations and Constructors
• String s // empty string for now -- its length
  is 0
• s new String() // String() is null
  constructor. It yields an empty //
  string for now whose length is 0
• s new String(hello) // initializes s to
  hello
• String s hello // initializes s to
  hello
• s2 new String (s1) // copy constructor
• String s hello world // String
  concatenation
• s1.equals (s2) // tests equality of contents
• s1 s2 // tests if both refer to same
  object in memory
• Knows its own length! (e.g. s.length)
• Array of Strings String Pets dog, cat,
  fish

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Some Java Operators Deitel, p. 271 complete
list is in Appendix C
Precedence Operator higher up the chart is
evaluated before operator lower down the chart
Associativity Order of evaluation for operators
of equal precedence
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Expressions

• Sequence of operators and operands that specifies
  a computation
• May result in a value (e.g., 123, true)
• May cause side-effects (e.g., change a value)
• Compound expressions (e.g., (ab)c))
• Includes literals (numbers or strings)

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Java Expression BNF
expression numeric_expression
testing_expression
logical_expression string_expression
bit_expression casting_expression
creating_expression
literal_expression "null"
"super" "this" identifier
( "(" expression ")" ) ( expression
( ( "(" arglist ")" ) ( ""
expression "" ) ( "." expression )
( "," expression ) ( "instanceof" (
class_name interface_name ) ) ) )
From http//cuiwww.unige.ch/db-research/ Enseignem
ent/analyseinfo/BNFweb.html
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Statements

• Smallest executable unit
• Declaration statements
• Control statements
• Assignment statements
• Method invocation
• Compound statement (block)
• Semicolon-separated list of statements
• Enclosed in curly brackets
• Deitel calls it a block only if it has
  declarations of its own

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Java Abstract Windowing Toolkit GUI Components
(from java.awt package)

• java.awt.Graphics (see list on p. 530-531)
• Given an object g of Graphics class
• g.setColor( Color.red ) // Sets current drawing
  color to red
• g.drawString(hello, 200, 25) // Draws String
  starting at (200,25)
• g.drawLine(20, 28, 40, 10 ) // Draws line from
  (20,28) to (40,10)
• g.fillRect(100, 5, 20, 15) // Draws filled
  rectangle whose upper left
• 
  // corner is at (100, 5). Width 20.
  Height 15
• g.drawOval(60, 9, 20, 13) // Draws oval whose
  bounding box upper left
• 
  // corner is at (60, 9). Width 20.
  Height 13

uses current color
(0,0)
x
y
hello
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Java Swing GUI Components(from javax.swing
package)

• javax.swing.JOptionPane
• Dialog box
• message
• error
• information
• warning
• question
• plain
• input
• javax.swing.JTextArea
• javax.swing.JScrollPane