Internet and Java Revolutions Impact on Education

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Internet and Java Revolutions Impact on Education

Rajkumar School of Computing Queensland
University of Technology Brisbane,
Australia Email rajkumar_at_fit.qut.edu.au URL
http//www.fit.qut.edu.au/rajkumar
2
Motivation

• Potential delivery sites are widely distributed
• Information is rapidly changing
• Connections to the Internet have become
  ubiquitous
• Different learners have different needs

3
Agenda

• Internet and its Evolution
• Internet Tools
• Web and its Programming
• Internet as a delivery Vehicle
• Java for Internet Programming
• Java Nuts and Bolts
• Java Platform
• Developing Applets and Applications
• Challenges and Future Directions

4
What is the Internet ?

• It is a global network of computers
• that communicate with each other
• using a variety of protocols and
• overcoming various communication
• barriers.
• It is like International Telephone
• System

5
Internet Technology Evolution

• Internet is much bigger than what we think
• More than 25 years old
• More than doubling every year
• Technology effect
• suddenly every body sees the need for a
  technology
• like the radio or the TV
• 10 terabytes flows everyday

6
Installed base and Growth rate for telephone
lines, mobile phones, and Internet hots
Installed, 1995 1994-95 Growth
Rates () Income Group/ Phone
Mobile Internet Phone Mobile
Internet Region Lines Phones
Hosts Lines Phones Hosts Lower
Income 2.0 0.12 1.35 35.7 135.1 246.0 Lower-
Middle 9.1 0.33 73.31 8.7 105.1 167.0 Upper -
Middle 14.5 1.34 380.13 6.4 66.8 111.9 High 53.
2 8.70 10749.23 3.6 55.6 97.0 Africa 1.7 0.09 69
.14 7.9 60.5 81.4 Americas 29.0 5.17 8359.58 5.
4 42.3 91.5 Asia 5.4 0.62 121.70 14.7 108.3 150.
0 Europe 33.0 3.04 2732.24 3.6 59.5 112.2 Oceans
39.7 9.55 12845.55 4.0 85.7 88.8 World 12.1 1.
56 1661.89 7.0 60.4 97.8
Source ACM, Nov, 97 (phones, international
telecommunication union, hosts, network Wizards
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Internet

• Use of internet advertisement/elections/newspapers
  
• information is public
• Ubiquitous technology
• Network is the computer
• Intranets - internal TCP/IP nets
• PC accounts for 55 of total IT
• Applications tied to platform - API lock-in

8
Internet Evolution
Internet everywhere Internet appliances Price
based services Live communities ? ? ? ? ? ? ?
On line connects to internet Secure
payments Multi media Authoring Java VRML HTML
File mail TCP/IP Webpages Netscape
10 of Market
20 of Market
Total Market
9
Early Internet

• Early Internet supported only email .
• File Transfer Protocol development - ftp sites.
• Network News was added to the Internet.
• Archie - A program to canvass anonymous ftp sites
  and create a database of what is available
• Gopher- A menu-driven interface used to search
  for information.
• Archie and Gopher could answer questions only
  like what FTP server contains info about xxxx

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World Wide Web

• World Wide Web conceptualized by Tim Berners-Lee
  at CERN in Switzerland
• Concept of Hypertext led to the development of
  the Hypertext Markup Language (HTML)
• Tim Berners-Lee proposed the Browser program
• Scientists at CERN designed a TCP/IP based
  protocol to share Hypertext information called
  HTTP.
• WWW officially is described as a Wide-area
  hypermedia information retrieval initiative
  aiming to give universal access to a large
  universe of documents.

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Viewing WWW pages

• View text, graphics, pictures, sounds, video
• Web Browser
• HyperText Markup Language (HTML)
• Computer Independent
• Operating System Independent

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Web Browsers

• Netscape Navigator
• Microsoft Internet Explorer
• Omni Web
• NCSA Mosaic
• Lynx (text only)

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Internet Organization

• Truly world-wide
• Multiple communication media types

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Internet Organization
Domains .edu .org .com .mil .biz Computers fi
fe.engr.vt.edu www.engr.vt.edu
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WWW Organization
Client
Client
Server
Server
Server
Client
Server
Client
Client
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Generating Web Pages

• Simple Text Editor
• Word Processor or other tool export
• e.g., Internet Assistant for Microsoft Word
• HTML Editor
• Open file in Netscape Composer
• Last step is to put the file(s) on an HTML server

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HTML

• Hypertext -A little Hype and a Little Text.
• Hypertext point to information which can be local
  or remotely located.
• HTML -Derivative of the SGML( Standard
  Generalized Markup Language).
• HTML -information , commands for the Browser for
  formatting documents.
• HTML -The de-facto language for publishing on the
  Internet.
• Hypermedia- Hyper-links to Multimedia.

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Internet Tools

• Browsers- A tool used to view documents on the
  WWW
• Web servers - Machines which run the HTTP-server
  Software that respond to HTTP requests which it
  receives
• Authoring Tools - Editors specially made for
  editing HTML documents
• Filters -Tools to convert legacy documents to
  HTML format
• Scripting -Languages used for scripting
• WAIS- Wide Area Information Servers (WAIS) for
  indexing and doing full text searches

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How does the Web work ?

• Web -Designed around Client/Server Architecture
• Web Clients ( Web Browsers ) -send requests for
  documents to any Web Server
• Web Server -Program that responds to HTTP
  requests
• Hyperlink
• Web client connects to the specified Web Server
• The server responds by sending the information
  asked for
• The Browser formats the received HTML data and
  displays it

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How does the Web Work
Send the INFORMATION ABOUT C-DAC ACTS
HTTP
The client sends an HTTP message to a
computer running a Web Server program and asks
for a document
The information about C-DAC ACTS
The web server sends the hypermedia HTML
documents to the client. You end up seeing the
document on your screen
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HTML document

• ltHTMLgt
• ltTITLEgtCentre for Development of Advanced
  Computing
• lt/TITLEgt
• ltBODY BGCOLORE7CCCC TEXT000000
  LINK0000FFgt
• ...
• ...
• ltA HREFmailtowebmaster_at_cdacb.ernet.ingt
  webmasterlt/Agt
• lt/BODYgt
• lt/HTMLgt

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(No Transcript)
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URLs

• URLs- The Hypertext links we use today are known
  as Universal Resource Locator
• URLs-Each name is unique across the Internet
• An URL looks like this
• http//system.domain.ext999/dir1/dir2/dir3/file.h
  tml?blue
• Parts of a URL are,
• Service type, System Name, Port, Directory path,
  Filename,Search Components or Variables
• Service type, System Name, Directory path are the
  required parts of the URL

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CGI (Common Gateway Interface)

• CGI makes the Web a Two-way interface
• CGI -lets the user run a script when a web page
  is accessed
• Information from the Web Client is received
  through simple fill-in-the-forms kind of
  interface
• FORMS - Integrates data sheets, menus , check
  boxes
• CGI makes the Web interactive
• CGI -complicated to setup ,requires PERL
  knowledge
• HTML books talk less about CGI

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Authoring tools and Filters

• Authoring tools- Editors for HTML documents
• Editors similar to WYSIWYG word processing
  programs
• Semi-WYSIWYG or completely WYSIWYG
• Provide syntax checking and correction
• Filters -Convert legacy documents to HTML format
• Filters are useful when the documents already
  exist
• Authoring tools- HoTMetaL, HTML Assistant
  -Shareware

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Preconfigured v/s Integrated Internet Products

• Integrated Internet Products- From multiple
  vendors
• Preconfigured Systems- Web Server and a Client
  ready to use
• Suns Netra Internet Server
• SGIs WebFORCE Indy and WebFORCE Challenge S
• Apples Internet Server Solution
• DECs Internet AlphaServer
• Integraphs Web Server 10

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Future Directions

• Additions to HTML (Grammar, Maths, Display
  control)
• VRML (Virtual Reality Markup Language)
• Security - Using Scrambling and Encryption
• Common Client Interface (CCI)- Allows Clients to
  pass information back and forth between the
  Browser and the External Viewer
• Charge Mechanisms
• Performance Enhancements- Sending a page and
  graphics for that page in one connection

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Internet in Education
Creating Your Own Page HTML Tags (Title,
Body, images, etc.) Basic HTML code file
structure Links and Anchors Linking it
elsewhere Moving around the WWW Making
it all Look Pretty Use components such as
- WWW Forms, Frames, Sound, Video, -
Animation, WWW Plugins Make web attractive
through Adding web applications -
customer enquiry - Free applications
Institution Web Site - about the
university - faculties and department
details - research facilities, area, and
groups - faculty members details with their
publications Admission Process - course
announcement, - making available details of
course - admission applications, -
announcement of selection University
Facilities - computing facilities,
accommodation, recreation, etc.. Teaching
Process - Use of WWW in the Curriculum -
Homework and Quizzes - Virtual Classroom -
Virtual Lectures - Student Interaction - Q
A
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Internet as a delivery Vehicle
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Interesting URLs

• http//www.whitehouse.gov ( The WhiteHouse)
• http//www.w3.org (Everything about the WWW)
• http//sunsite.unc.edu (Software on Sun)
• http//www.indnet.org (India Net Foundation
  Services)
• telnet//www.arbornet.org (Free Public Access
  Unix System)
• http//www.infoseek.com (Search engines, Add URL)
• http//www.infophil.com (World Alumni on the net)
• http//www.rocketmail.com (Free Email )
• http//members.tripod.com (Free Website,2MB
  space)
• http//www.bangaloreonline.com (Offers virtual
  web servvices for compinies to host their
  website).
• http//www.prajavani.com (Kannada news paper on
  web)

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Class Sites To Visit

• http//truth.phil.vt.edu/wwwcourses.html
• http//http//fiddle.visc.ece.vt.edu/courses/ee250
  4/
• http//adept.stanford.edu/
• http//www.aoe.vt.edu/aoe5104.html
• http//nersp.nerdc.ufl.edu/cgs2422/
• http//www.sloan.org/oakley/misc/IMNews.html
• http//www.eng.fsu.edu/net98.html

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API Bottleneck
MAC
PC
LAN
LAN
Server
Network
SUN
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The OS - Platform lock
Applications tied to OS OS tied to Platform
Application
Application
OS
Application
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The Web
Seeded by HTML from CERN Revolutionised by
MOSAIC Standardised, universal interface to
data Graphical
Application
Application
BROWSER
OS
OS
OS
OS
Application
Application
Broadcast capability - publish once, reach
millions
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Making life easier!

• Data on the web
• Browser platform independent
• Click on application - run on any machine
• Java the programming language of the 21 century

36
Java and Java Computing
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Java - An Introduction

• Java - The new programming language from Sun
  Microsystems
• Java -Allows anyone to publish a web page with
  Java code in it
• Java - CPU Independent language
• Created for consumer electronics
• Java - James , Arthur Van , and others
• Java -The name that survived a patent search
• Oak -The predecessor of Java
• Java is C --

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Java From 10,000 Ft.

• According to the world, Java is...
• According to Sun, Java is...
• On closer inspection, Java is

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According to the World, Java Is...

• Snazzy Web pages
• The cross-platform language we want
• The rest-of-the-worlds answer to Bill
• The C replacement we need
• The C replacement we dont need
• A bunch of hype

40
According to Sun, Java is...

• Simple and Powerful
• Object Oriented
• Portable
• Architecture Neutral
• Distributed
• Multi-threaded
• Robust, Secure/Safe
• Interpreted
• High Performance
• Dynamic pogramming language/platform.

Buzzword compliant!
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On Closer Inspection, Java is...

• Simple
• Pure
• Portable
• Surprisingly effective

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As a whole, Java is a Comprehensive Programming
Solution

• Object Oriented
• Portable
• High Performance
• Geared for Distributed Environments
• Secure

43
Java as Object Oriented

• Objects all the way down
• Simple and Familiar C Lite
• No Pointers!
• Garbage Collector
• Dynamic Binding
• Single Inheritance with Interfaces

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Java as Portable

• Unlike other language compilers, Java complier
  generates code (byte codes) for Universal
  Machine.
• Java Virtual Machine (JVM) Interprets bytecodes
  at runtime
• Architecture Neutral
• No Link Phase
• Higher Level Portable Features AWT, Unicode

45
Total Platform Independence
JAVA COMPILER
(translator)
JAVA BYTE CODE
(same for all platforms)
JAVA INTERPRETER
(one for each different system)
Windows 95
Macintosh
Solaris
Windows NT
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Java Write Once, Run Anywhere
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Architecture Neutral Portable

• Java Compiler -Java source code to bytecode
• Bytecode - an intermediate form, closer to
  machine representation
• A virtual machine on any target platform
  interprets the bytecode
• Porting the java system to any new platform
  involves writing an interpreter that supports the
  Java Virtual Machine
• The interpreter will figure out what the
  equivalent machine dependent code to run

48
Java as High Performance

• JVM uses lean and mean bytecodes
• Small binary class filtes
• Just-in-time Compilers
• Multithreading
• Native Methods

49
Java in the World of Distributed Computing

• Class Loader
• Lightweight Binary Class Files
• Multithreading
• Dynamic
• Good communication constructs
• Secure

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Java as Secure

• Language designed as safe
• Strict compiler
• Dynamic Runtime Loading (Verifier)
• Runtime Security Manager

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Object Oriented Languages -a Comparison
52
Java better than C ?

• No Typedefs, Defines, or Preprocessor
• No Global Variables
• No Goto statements
• No Pointers
• No Unsafe Structures
• No Multiple Inheritance
• No Operator Overloading
• No Automatic Coercions
• No Fragile Data Types

?
53
Basic Data Types

• Types
• boolean either true of false
• char 16 bit Unicode 1.1
• byte 8-bit integer (signed)
• short 16-bit integer (signed)
• int 32-bit integer (signed)
• long 64-bit integer (singed)
• float 32-bit floating point (IEEE 754-1985)
• double 64-bit floating point (IEEE 754-1985)
• String (class for manipulating strings)
• Java uses Unicode to represent characters
  internally

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• Java Integrates
• Power of Compiled Languages
• and
• Flexibility of Interpreted Languages

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Two Types of JavaApplications

• Different ways to write/run a Java codes are
  
• Application- A stand-alone program that can be
  invoked from command line . A program that has a
  main method
• Applet- A program embedded in a web page , to be
  run when the page is browsed . A program that
  contains no main method
• Application -Java interpreter
• Applets- Java enabled web browser (Linked to HTML
  via ltAPPLETgt tag. in html file)

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Java Environment/ Life Cycle of Java Code
Runtime Environment
Compile-time Environment
Class Loader Bytecode Verifier
Java Class Libraries
Java Source (.java)
Java Bytecodes move locally or through network
Java Virtual machine
Java Compiler
Runtime System
Java Bytecode (.class )
Operating System
Hardware
57
Java Development Kit

• javac - The Java Compiler
• java - The Java Interpreter
• jdb- The Java Debugger
• appletviewer -Tool to run the applets
• javap - to print the Java bytecodes
• javaprof - Java profiler
• javadoc - documentation generator
• javah - creates C header files

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Hello Internet

• // hello.java Hello Internet program
• class HelloInternet
• public static void main(String args)
• System.out.println(Hello Internet)

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Program Processing

• Compilation
• javac hello.java
• results in HelloInternet.class
• Execution
• java HelloInternet
• Hello Internet

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Simple Java Applet

• // HelloWorld.java A sample applet
• import java.applet.Applet
• public class HelloWorld extends Applet
• public void paint(Graphics g)
• g.drawString(Hello World !,25,25)

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Calling an Applet

• ltHTMLgt
• ltTITLEgt Hello Worls Applet lt/TITLEgt
• ltAPPLET codeHelloWorld.class width500
  height500gt
• lt/APPLETgt
• lt/HTMLgt

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Execution of Applets
4
2
5
3
1
Accessing from CRAY Corp. (USA)
APPLET Development hello.java AT CDAC-India
The browser creates a new window and a new
thread and then runs the code
hello.class AT C-DACS WEB SERVER
Create Applet tag in HTML document
Hello Java
ltapp Hellogt
The Internet
Hello
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Web Perspective

• How did Web interactions work?
• How do they work with Java?
• Distributed Java objects and the Web

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Classical Web Perspective
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Java Web Perspective
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Significance of downloading Applets

• Interactive WWW
• Flashy animation instead of static web pages
• Applets react to users input and dynamically
  change
• Display of dynamic data
• WWW with Java - more than a document publishing
  medium
• http//www.javasoft.com/applets/alpha/applets/Stoc
  kDemo/standalone.html

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Power of Java and the Web

• Deliver applications, not just information
• Eliminate porting
• Eliminate end-user installation
• Slash software distribution costs
• Reach millions of customers - instantly

68
Lifecycle of Java Code
69
Bytecode Verifier

• Called when class is first loaded in runtime
  environment
• Verifies bytecodes meet certain set of properties
• Verifier uses Theorem Prover
• Verified code runs faster
• After verification, interpreter defines memory
  layout

70
Class Loader

• Unique Namespace for each origin
• Local namespace classes are called built-ins
• Prevents class spoofing

71
Security Manager

• Prevents unauthorized disk read/writes
• Restricts network access
• Other access restrictions (native methods)
• Implementation is browser dependent

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General Language Features

• C/C like syntax
• No pointers
• Objects all the way down
• Objects request services of other objects through
  messages
• Messages result in invocation of class methods

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Removed From C

• Operator overloading
• Pointers and Array/pointers
• Multiple-inheritance of implementation
• Enum, typedef, define
• Copy constructors, destructors
• Templates
• And other stuff....

74
Added or Improved over C

• Interfaces type Vs. class
• Garbage collection
• Exceptions (More powerful than C)
• Strings
• Instanceof
• Package
• Multi-threads

75
Declaring Classes

• class Queue
• Object data
• Queue (int size) // Constructor
• data new Objectsize
• void add(Object o)
• // add to array in class specific
  manner...
• // other methods

76
Inheritance in Java

• class PriorityQueue extends Queue
• PriorityQueue (int size) // Constructor
• super(size) // Call Queue constructor use
  data
• // Class specific initialization
• void add(Object o) // Overriden method
• // add to array in class specific
  manner...
• // other methods

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Creating and Using Objects

• PriorityQueue p new PriorityQueue(10) // Q of
  size 10
• String s This is a string
• p.add(s) // Add string to priority queue
• p.add(this) // Add object calling this code to
  queue...

78
Class Methods and Variables

• int pi Math.PI
• int theMax Math.max(x,6)
• Definitions
• public final static double PI
• 3.14159265358979323846
• public static int max(int a, int b)

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Access Rules

• public
• private
• protected
• package (Default - no keyword)

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Using Threads

• Define a Thread class
• public MyThread extends Thread
• public void run() // Override default
  method
• while (true) // do custom code
• .
• Using the thread
• MyThread t new MyThread()
• t.start() // Start the thread...
• Detailed discussion on Threads, later

81
Strings

• The language defines strings as objects
• doSomething("abc" "cde")
• doSomething(String s) ..
• String abc new String(Hello)
• System.out.println(abc)

82
Exceptions

• Try, catch, throw, finally
• try failure_Prone_Call()
• catch (File_Exception f) ....Handle f....
• finally do_This_Regardless()
• Exception signatures are checked void foo()
  throws TypeC
• Exceptions must be caught or declared
• Errors do not have to be caught
• Surprisingly effective at producing robust code

83
Exception Handling

• try
• // some code here...
• int x y/z
• catch (ArithmeticException e)
• System.out.println(Divide by zero error!)
• catch (Exception e)
• System.out.println(Some other error!)
• finally // Optional...
• z

84
More about Exceptions

• Very Strict Exception Handling Rules
• All methods that throw an exception must be
  caught or rethrown (except for runtime
  exceptions)
• Hierarchy of Exception classes
• Can create custom Exception classes
• Cause own exception with throw clause

85
Interfaces

• Interfaces are a way to declare an Abstract type
  without implementation
• Interfaces are like classes but without
  implementation
• Interfaces are expressions of pure designs only
• Example Interface
• interface sqrt
• int sqrt(int newint)
• Implementing an interface
• class myclass implements sqrt
• ..........

86
Interface Type and Sub-Type

• Pure type of a set of objects
• interface Observer
• void update (Observable o)
• Interfaces can form a graph
• interface List_Observer extends Observer
• void updateItem (int position)

87
Class Implements Interface

• Complete type/class separation possible
• class Order implements Observer
• public void update (Object o)
• // do stuff toupdate
• // data and other implementation
• Any object can support multiple interfaces
• Client can see its types separately or conjoined
• A powerful approach to design, roles,
  distribution, design patterns
• Takes a little bit of getting used to

88
Implementation Inheritance

• Single inheritance of implementation
• class X extends W implements E, F
• // Stuff in class X

89
Interfaces and Classes!
90
Uses of Interfaces

• There are considerable problems due to Multiple
  Inheritance
• Interfaces in a way add multiple inheritance to
  Java
• Interfaces may be extended too, more than once

91
Garbage Collected

• No more manual memory management
• class Recycler
• public void recycle ()
• Hashtable t
• for (int i0 ilt100 i)
• t new Hashtable()
• Significant elimination of programming bugs

92
instanceof and casts

• Run-time type query
• void foo (Object x)
• if (x instanceof Order)
• Order o (Order) x
• // ...Do stuff with o
• Can query for an interface or a class

93
Packages

• No more include
• package Shopper
• import java.awt.
• // define Shopper interfaces and classes
• Provides namespace and export features
• class, sub-class, intra-package, and inter
  package control
• Package typically maps to a directory

94
Packages and Utilities

• Packages - helps in organizeing classes i.e.,
  keep the class name space compartmentalized
• For Naming and Visibility
• Similar to C Class Libraries
• Bring in classes from other packages with the
  import keyowrd
• Ad hoc collection of utility classes
• Storing collection of objects
• Interfacing with low-level system functions
• Math functions (java.lang.Math)

95
Rich Object Environment

• Core Classes
• language
• Utilities
• Input/Output
• Low-Level Networking
• Abstract Graphical User Interface
• Internet Classes
• TCP/IP Networking
• WWW and HTML
• Distributed Programs

96
Main Packages

• java.lang
• java.util
• java.io
• java.awt
• java.awt.image
• java.applet
• java.net

97
java.lang Core Classes

• Base Class Object
• String
• String s This is number 6
• Math
• Math.sqrt(4.0)
• System
• System.out.println(An error occurred)
• System.exit(1)

98
java.lang Type Wrappers

• Literals int, double, boolean, char
• Literals wrapped in Classes Integer, Double,
  Boolean, Character
• Literals used for high performance
• Examples
• int x Integer.parseInt(6)
• Integer I new Integer(999)
• double dbl I.doubleValue()//Returns 999.000

99
java.io - Filtering input streams

• try // Open the file...
• DataInputStream dis new DataInputStream(
  new BufferedInputStream(
• new FileInputStream(myFile)) )
• // Read lines until EOF is reached...
• String s
• while((s dis.readLine()) ! null) //
  Read CR delimited lines
• System.out.println(s)
• dis.close()
• // Handle any exceptions caused by the
  process...
• catch (IOException e)
• System.out.println(e.getMessage())

100
GUI Programming in Java(AWT and Event Handling)
101
AWT - Abstract Windowing Toolkit

• Single Windowing Interface on Multiple Platforms
• Supports functions common to all window systems
• Uses Underlying Native Window system
• AWT provides
• GUI widgets
• Event Handling
• Containers for widgets
• Layout managers
• Graphic operations

102
AWT - Abstract Window Toolkit

• Portable GUI - preserves native look feel
• Standard GUI Components (buttons)
• Containers - Panels, Frames, Dialogs
• Graphics class for custom drawing
• Layouts responsible for actual positioning of
  components
• BorderLayout, GridLayout, FlowLayout, null layoit

103
Adding Components via Layouts

• setLayout(new BorderLayout())
• // Add text field to top
• add("North",new TextField())
• // Create the panel with buttons at the
  bottom...
• Panel p new Panel() // FlowLayout
• p.add(new Button("OK"))
• p.add(new Button("Cancel"))
• add("South",p)

104
Adding Components via Layouts
105
Popup Menu and Event Handling...

• //popup.java popup menu and event handling
• import java.applet.Applet
• import java.awt.
• import java.awt.event.
• public class popup extends Frame implements
  ActionListener, MouseListener
• TextField text1
• PopupMenu popup
• MenuItem menuitem1, menuitem2, menuitem3
• public popup()
• super( "Popup Menu" )
• setLayout(new FlowLayout())
• setBounds(10, 10, 300, 200 )
• setVisible(true)
• init()
• public void init()

106
Popup Menu and Event Handling...

• menuitem1 new MenuItem("CPU")
• menuitem1.addActionListener(this)
• menuitem2 new MenuItem("Disk")
• menuitem2.addActionListener(this)
• menuitem3 new MenuItem("Memory")
• menuitem3.addActionListener(this)
• popup.add(menuitem1)
• popup.add(menuitem2)
• popup.add(menuitem3)
• add(popup)
• text1 new TextField(20)
• text1.setBounds(20, 40, 120, 30 )
• add(text1)
• addMouseListener(this)
• public void mousePressed(MouseEvent e )
• if( e.getModifiers() ! 0 )
• popup.show(this, e.getX(), e.getY() )

107
Popup Menu and Event Handling

• public void mouseReleased( MouseEvent e )
• System.out.print("Mouse Released\n" )
• public void mouseEntered( MouseEvent e )
• System.out.print("Mouse Entered\n" )
• public void mouseExited( MouseEvent e )
• System.out.print("Mouse Exited\n" )
• public void actionPerformed( ActionEvent e )
• if( e.getSource() menuitem1 )
• text1.setText("CPU")
• if( e.getSource() menuitem2 )
• text1.setText("Disk")
• if( e.getSource() menuitem3 )
• text1.setText("Memory")
• public static void main( String args )
• popup p new popup()

108
Custom Drawing

• // MyApplet.java draws rectangle with yellow
  color fill
• import java.applet.
• import java.awt.
• public class MyApplet extends Applet
• public synchronized void paint(Graphics g)
• int x,y,width,height
• Dimension dm size()
• x dm.width/4
• y dm.height / 4
• width dm.width / 2
• height dm.height / 2
• // Draw the rectangle in the center with
  colors!
• g.setColor(Color.blue)
• g.drawRect(x,y,width,height)
• g.setColor(Color.yellow)
• g.fillRect(x 1,y 1,width - 2,height -
  2)

109
java.applet

• Applet
• Class representation of applet
• init() method called when first loaded
• start() when applets Web page becomes active
• stop() when user leaves Web Page
• Actually derived from AWT Panel
• AppletContext
• Hooks into Browser environment
• Can be used to link to another Web page

110
A sample Applet

• // HelloApplet.java for processing applet
  methods
• import java.awt.
• import java.applet.
• public class HelloApplet extends Applet
• public void init()
• System.out.println("init() method
  invoked")
• public void start()
• System.out.println("start() method
  invoked")
• public void paint( Graphics g )
• System.out.println("paint() method
  invoked")
• g.drawString( "Hello World", 24, 25 )
• public void stop()

111
Network/Socket Programming in Java
112
java.net

• Used to manage
• URL streams
• Client/server sockets
• Datagrams

113
Server side Socket Operations

• 1. Open Server Socket
• String server Socket slink
• DataOutputStream os
• DataInputStream is
• server new ServerSocket( PORT )
• 2. Wait for Client Request
• Socket client server.accept()
• 3. Create I/O streams for communicating to
  clients
• is new DataInputStream( client.getInputStream()
  )
• os new DataOutputStream( client.getOutputStre
  am() )
• 4. Perform communication with client
• Receiive from client String line
  is.readLine()
• Send to client os.writeBytes("Hello\n")
• 5. Close sockets client.close()
• For multithreade server
• while(true)
• i. wait for client requests (step 2 above)
• ii. create a thread with client socket as
  parameter (the thread creates streams (as in step
  (3) and does communication as stated in (4).
  Remove thread once service is provided.

114
Client side Socket Operations

• 1. Get connection to server
• client new Socket( server, port_id )
• 2. Create I/O streams for communicating to
  clients
• is new DataInputStream( client.getInputStream()
  )
• os new DataOutputStream( client.getOutputStre
  am() )
• 3. Perform communication with client
• Receiive from client String line
  is.readLine()
• Send to client os.writeBytes("Hello\n")
• 4. Close sockets client.close()

115
Echo Server Client..

• //client.java client interface to server
• import java.io.
• import java.net.
• public class client
• int port_id
• String server Socket slink
• DataOutputStream os
• DataInputStream is
• DataInputStream kbd
• public client( String args )
• server args0
• port_id Integer.valueOf(args1).intValue(
  )
• try
• slink new Socket( server, port_id )
• os new DataOutputStream(
  slink.getOutputStream() )
• is new DataInputStream(
  slink.getInputStream() )

116
Echo Server Client..

• catch( UnknownHostException e )
• System.err.println( "Don't know about
  host " )
• System.exit(1)
• catch( IOException e )
• System.err.println( "Could not get I/O for the
  connection to "server)
• System.exit(1)
• void communicate()
• while(true)
• try
• System.out.print("Enter Input ltend to
  stopgt ")
• String line kbd.readLine()
• os.writeBytes( line"\n" )

117
Echo Server Client..

• if( line.equals("end") )
• os.close() is.close() slink.close()
• break
• String line2 is.readLine()
• System.out.println("Output "line2)
• catch( IOException e )
• System.out.println(e)
• public static void main( String args )
• if( args.length lt 2 )
• System.out.println("Usage java client
  server_name port_id" )
• System.exit(1)
• client cln new client( args )

118
Echo Server ...

• // server.java echo server
• import java.io.
• import java.net.
• public class server
• // public final static int PORT 4779
• public static void main( String args )
• ServerSocket server null
• DataOutputStream os null
• DataInputStream is null
• boolean shutdown false
• if( args.length lt 1 )
• System.out.println( "Usage java server
  port_num" )
• System.exit( 1 )
• int PORT Integer.valueOf(args0).intValue
  ()
• try

119
Echo Server ...

• catch( IOException e )
• System.err.println( "Could not get I/O for
  the connection to ")
• while(!shutdown)
• if( server ! null )
• try
• Socket client server.accept()
• System.out.println("Connected")
• InetAddress cip client.getInetAddres
  s()
• System.out.println( "Client IP Addr
  "cip.toString())
• is new DataInputStream(
  client.getInputStream() )
• os new DataOutputStream(
  client.getOutputStream() )
• for()
• String line is.readLine()

120
Echo Server ...

• if( line.startsWith("end" ) )
• shutdown true
• break
• os.writeBytes(line.toUpperCase())
• os.writeBytes("\n")
• System.out.println(line)
• is.close() client.close()
• catch( UnknownHostException e )
• System.err.println( "Server Open fails" )
• catch( IOException e )
• System.err.println( "Could not get I/O for the
  connection to"args0)

121
Echo Server

• System.out.println( "Server Down" )
• try
• server.close()
• catch(IOException e)

122
Multithreading in Java(A built-in feature in
Java)
123
What are Threads?

• Thread is a piece of code that can execute in
  concurrence with other threads.
• It is a schedule entity on a processor

• Local state
• Global/ shared state
• PC
• Hard/Software Context

Thread Object
124
Single and Multithreaded Processes
Single-threaded Process
Multiplethreaded Process
Threads of Execution
Multiple instruction stream
Single instruction stream
Common Address Space
125
OSMulti-Processing, Multi-Threaded
Threaded Libraries, Multi-threaded I/O
Better Response Times in Multiple Application
Environments
Higher Throughput for Parallelizeable Applications
126
Threaded Process Model
THREAD STACK
SHARED MEMORY
THREAD DATA
Threads within a process
THREAD TEXT

• Independent executables
• All threads are parts of a process hence
  communication
• easier and simpler.

127
Levels of Parallelism Thread Granularity
Code-Granularity Code Item Large grain (task
level) Program Medium grain (control
level) Function (thread) Fine grain (data
level) Loop Very fine grain (multiple
issue) With hardware
Task i-l
Task i
Task i1
func1 ( ) .... ....
func2 ( ) .... ....
func3 ( ) .... ....

• Task
• Control
• Data
• Multiple Issue

a ( 0 ) .. b ( 0 ) ..
a ( 1 ).. b ( 1 )..
a ( 2 ).. b ( 2 )..

x
Load
128
Multithreading - Uniprocessors

• Concurrency Vs Parallelism

• Concurrency

P1
CPU
P2
P3
time
Number of Simulatneous execution units gt no of
CPUs
129
Multithreading - Multiprocessors
Concurrency Vs Parallelism
CPU
P1
CPU
P2
CPU
P3
time
No of execution process no of CPUs
130
Threads

• Java has built in thread support for
  Multithreading
• Synchronization
• Thread Scheduling
• Inter-Thread Communication
• currentThread start setPriority
• yield run getPriority
• sleep stop suspend
• resume
• Java Garbage Collector is a low-priority thread

131
Threading Mechanisms...

• Create a class that extends the Thread class
• Create a class that implements the Runnable
  interface

132
1st method Extending Thread class

• 1st Method Extending the Thread class
• class MyThread extends Thread
• public void run()
• // thread body of execution
• Creating thread
• MyThread thr1 new MyThread()
• Start Execution
• thr1.start()

133
2nd method Threads by implementing Runnable
interface

• class ClassName implements Runnable
• .....
• public void run()
• // thread body of execution
• Creating Object
• ClassName myObject new ClassName()
• Creating Thread Object
• Thread thr1 new Thread( myObject )
• Start Execution
• thr1.start()

134
Multi-Threaded

• Thread and its subclasses run one thread per
  instance
• class MyThread extends Thread public void run
  () ...Start running
• Any Runnable object can wrap a thread around
  itself
• class Server implements Runnable Thread t
  Server () t new Thread(this) .
• public void run () ...Start running
• Thread control Thread.start(), Thread.stop()

135
Manipulation of Current Thread

• // CurrentThreadDemo.java
• class CurrentThreadDemo
• public static void main(String arg)
• Thread ct Thread.currentThread()
• ct.setName( "My Thread" )
• System.out.println("Current Thread "ct)
• try
• for(int i5 igt0 i--)
• System.out.println(" " i)
• Thread.sleep(1000)
• catch(InterruptedException e)
• System.out.println("Interrupted.")
• Run
• Current Thread ThreadMy Thread,5,main
• 5

136
Creating new Thread...

• // ThreadDemo.java
• class ThreadDemo implements Runnable
• ThreadDemo()
• Thread ct Thread.currentThread()
• System.out.println("Current Thread "ct)
• Thread t new Thread(this,"Demo Thread")
• t.start()
• try
• Thread.sleep(3000)
• catch(InterruptedException e)
• System.out.println("Interrupted.")
• System.out.println("Exiting main thread.")

137
...Creating new Thread.

• public void run()
• try
• for(int i5 igt0 i--)
• System.out.println(" " i)
• Thread.sleep(1000)
• catch(InterruptedException e)
• System.out.println("Child interrupted.")
  
• System.out.println("Exiting child
  thread.")
• public static void main(String args)
• new ThreadDemo()
• Run
• Current Thread Threadmain,5,main
• 5
• 4
• 3

138
Thread Priority...

• // HiLoPri.java
• class Clicker implements Runnable
• int click 0
• private Thread t
• private boolean running true
• public Clicker(int p)
• t new Thread(this)
• t.setPriority(p)
• public void run()
• while(running)
• click
• public void start()
• t.start()
• public void stop()
• running false

139
...Thread Priority

• class HiLoPri
• public static void main(String args)
• Thread.currentThread().setPriority(Thread.MA
  X_PRIORITY)
• Clicker Hi new Clicker(Thread.NORM_PRIORIT
  Y2)
• Clicker Lo new Clicker(Thread.NORM_PRIORIT
  Y-2)
• Lo.start()
• Hi.start()
• try Thread.sleep(10000)
• catch (Exception e)
• Lo.stop()
• Hi.stop()
• System.out.println(Lo.click " vs. "
  Hi.click)
• Run1 (on Solaris)
• 0 vs. 956228
• Run2 (Window 95)

140
Threads Need Synchronization

• Server instances lock themselves at method-level
• class Buffer // synchronize on buffer instance
  public synchronized void put (int i) ...
• public synchronized int get () . void safe () .
• Client instance locks a server object before
  using it
• synchronized (array_to_sort) ..... wait() //
  within synchronized methodnotify()
• notifyall() // wake up from a wait

141
Monitor model (for Syncronisation)
Method 1
Method 2
Key
Block 1
Threads
Monitor (synchronised) solves race-condition
problem
142
Threads Synchronisation...

• // Synch.java race-condition without
  synchronisation
• class Callme
• // Check synchronized and unsynchronized
  methods
• / synchronized / void call(String msg)
• System.out.print(""msg)
• try Thread.sleep(1000)
• catch(Exception e)
• System.out.println("")
• class Caller implements Runnable
• String msg
• Callme Target
• public Caller(Callme t, String s)
• Target t
• msg s

143
...Threads Synchronisation.

• public void run()
• Target.call(msg)
• class Synch
• public static void main(String args)
• Callme Target new Callme()
• new Caller(Target, "Hello")
• new Caller(Target, "Synchronized")
• new Caller(Target, "World")
• Run 1 With unsynchronized call method (race
  condition)
• HelloSynchronizedWorld
• Run 2 With synchronized call method
• Hello
• Synchronized

144
Queue (no inter-threaded communication)...

• // pc.java produce and consumer
• class Queue
• int n
• synchronized int get()
• System.out.println("Got "n)
• return n
• synchronized void put(int n)
• this.n n
• System.out.println("Put "n)
• class Producer implements Runnable
• Queue Q
• Producer(Queue q)
• Q q

145
Queue (no inter-threaded communication)...

• public void run()
• int i 0
• while(true)
• Q.put(i)
• class Consumer implements Runnable
• Queue Q
• Consumer(Queue q)
• Q q
• new Thread( this, "Consumer").start()
• public void run()
• while(true)
• Q.get()

146
...Queue (no inter-threaded communication).

• class PC
• public static void main(String args)
• Queue Q new Queue()
• new Producer(Q)
• new Consumer(Q)
• Run
• Put 1
• Got 1
• Got 1
• Got 1
• Put 2
• Put 3
• Got 3
• C

147
Queue (interthread communication)...

• // PCnew.java produce-consumenr with interthread
  communication
• class Queue
• int n
• boolean ValueSet false
• synchronized int get()
• try
• if(!ValueSet)
• wait()
• catch(InterruptedException e)
• System.out.println("Got "n)
• ValueSet false
• notify()
• return n

148
Queue (interthread communication)...

• synchronized void put(int n)
• try
• if(ValueSet)
• wait()
• catch(InterruptedException e)
• this.n n
• System.out.println("Put "n)
• ValueSet true
• notify()
• class Producer implements Runnable
• Queue Q
• Producer(Queue q)
• Q q

149
Queue (interthread communication)...

• public void run()
• int i 0
• while(true)
• Q.put(i)
• class Consumer implements Runnable
• Queue Q
• Consumer(Queue q)
• Q q
• new Thread( this, "Consumer").start()
• public void run()
• while(true)
• Q.get()

150
...Queue (no interthread communication).

• class PCnew
• public static void main(String args)
• Queue Q new Queue()
• new Producer(Q)
• new Consumer(Q)
• Run
• Put 0
• Got 0
• Put 1
• Got 1
• Put 2
• Got 2
• Put 3
• Got 3
• Put 4

151
Deadlock...

• // DeadLock.java
• class A
• synchronized void foo(B b)
• String name Thread.currentThread().getName
  ()
• System.out.println(name " entered
  A.foo")
• try
• Thread.sleep(1000)
• catch(Exception e)
• System.out.println(name " trying to call
  B.last()")
• b.last()
• synchronized void last()

152
Deadlock...

• class B
• synchronized void bar(A a)
• String name Thread.currentThread().getName
  ()
• System.out.println(name " entered
  B.bar")
• try
• Thread.sleep(1000)
• catch(Exception e)
• System.out.println(name " trying to call
  A.last()")
• a.last()
• synchronized void last()

153
...Deadlock.

• class DeadLock implements Runnable
• A a new A() B b new B()
• DeadLock()
• Thread.currentThread().setName("Main
  Thread")
• new Thread(this).start()
• a.foo(b)
• System.out.println("Back in the main
  thread.")
• public void run()
• Thread.currentThread().setName("Racing
  Thread")
• b.bar(a) System.out.println("Back in the
  other thread")
• public static void main(String args)
• new DeadLock()
• Run
• Main Thread entered A.foo
• Racing Thread entered B.bar

154
Threads in Action...Cooperative threads - File
Copy
reader() - - - - - - - - - - lock(buffi) read
(src,buffi) unlock(buffi) - - - - - - - - -
-
writer() - - - - - - - - - - lock(buffi) writ
e(src,buffi) unlock(buffi) - - - - - - - -
- -
buff0
buff1
Cooperative Parallel Synchronized Threads
155
Threads in Action... Multithreaded Server
Server Process
Client Process
Server Threads
Client Process
User Mode
Kernel Mode
Message Passing Facility
156
A Look Inside the Java Platform
Applets and Applications
Java Base API Java Base Classes
Java Standard Extension API Java Standard
Extension Classes
The Java Base Platform (in black)
Java Virtual Machine
Porting Interface
Network
Java on a Browser
Java on a Desktop OS
Java on a Smaller OS
Java on JavaOS
157
Java Applications!

• Java applications are now available
• Cost of manfg zero, cost of distribution zero,
  cost of marketing zero!
• Hot Java is lean - loads everything else from the
  net.
• Java itself is small - 40k to 225k
• New class of small machines will emerge
• Java on cellular phones, credit cards, washing
  machines, and everywhere ?

158
Universal Interface
Web Servers with JAVA applications
Internet
Clients running any OS on any platform
159
Java on my platform ?

• Sun (SPARC) ftp//java.sun.com
• Sun(x86) ftp//xm.com/pub/
• IBM(Aix, OS/2)ftp//ncc.hursley.ibm.com/javainfo
• DEC(Alpha OSF/1) http//www.gr.osf.org8001/projec
  ts/web/java/
• SGI http//liawww.epfl.ch/simon/java/irix-jdk.htm
  l
• HP http//www.gr.osf.org8001/projects/web/java
• Linux http//www.blackdown.org
• AT T http//www.gr.osf.org8001/projects/web/jav
  a
• Windows 3.1 http//www.alphaworks.ibm.com

160
Java Development Tools (Present and Planned)
161
Suns Java WorkShop

• JDK
• Compiler and runtime environment
• Class Libraries
• Documentation
• javadoc - Automated Documentation
• Takes comments and converts to HTML
• IDE Visual Java, and integrated tools, JavaBeans
• Other Products and API JavaHelp, Java Card, Java
  Blend, JavaOS, Java Mail, Java Management, Java
  Electronic Commerce Framework
• Java Enterprise API Java Naming and Directory
  Interface, Java IDL, JDBC, RMI and Object
  Serialization

162
Symantec Cafe 1.0 (Released)

• Full IDE for Windows 95/NT
• Graphic Development Tools
• Two Compilers
• Debugger
• Class Browser

163
Microsoft Jakarta (Planned)

• Visual C type interface
• Will Support ActiveX/COM
• Internet Explorer 3.0 will have Just-In-Time Java
  compiler

164
Borland JBuilder

• Visual RAD workbench for maximum productivity.
• Rapid Application Development (RAD) and Open
  Component Architecture patterned after Delphi.
• 100 JavaBean components, with source code, for
  drag-and-drop applications.
• Beans Express--easiest way to create
  industry-standard Java-Bean components.
• DataExpress -- the fastest way to build business
  and database appplications.
• Borland DataGateway for Java connectivity to all
  major database servers.
• Multi-tier applications with integrated RMI and
  CORBA.
• Versions Standard, Professional, Client/Server

165
Challenges Possible Directions

• Performance
• AWT - need better GUI!
• Maintaining Interoperability
• Security - current restrictions limit what can be
  done
• Native Compilers
• Is Portability that Important?

166
Comments

• Java is a fun and easy programming language
• Portability Mediocrity?
• Java will become a programming language of
  choice, but may take on a final form that will
  surprise many!

167
JDBC

• Java API for Relational Databases
• Being standardized by all major players

168
Javascript and Java (Preview)

• Javascript can control Java applets
• Static data accessible as properties of applet
• var i Bank.Account.count
• Public methods invocable on Java instances
• Provided those instances are accessible through
  the Applet
• Applet is accessible through document
• document.applet_Name_Attribute.do_S