Internet and Java Revolutions
Impact on Education
(c) Rajkumar
Rajkumar
School of Computing
Queensland University of Technology
Brisbane, Australia
Email: [email protected]
URL: http://www.fit.qut.edu.au/~rajkumar
1
Motivation
(c) Rajkumar
Potential delivery sites are widely distributed
 Information is rapidly changing
 Connections to the Internet have become
ubiquitous
 Different learners have different needs

2
Agenda
(c) Rajkumar
 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
3
What is the Internet ?
(c) Rajkumar
•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
4
Internet Technology
Evolution
(c) Rajkumar
 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
5
Installed base and Growth rate for telephone
lines, mobile phones, and Internet hots
(c) Rajkumar
Income Group/
Region
Installed, 1995
Phone Mobile Internet
Lines
Phones Hosts
1994-95 Growth Rates (%)
Phone Mobile Internet
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
6
Internet
(c) Rajkumar
 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
7
Internet Evolution
(c) Rajkumar
File & mail
TCP/IP
Webpages
Netscape
10% of
Market
On line connects
to internet
Secure payments
Multi media Authoring
Java
VRML
HTML
20% of
Market
Internet everywhere
Internet appliances
Price based services
Live communities
?
?
?
?
?
?
?
Total
Market
8
Early Internet
(c) Rajkumar
•
•
•
•
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” ‘
9
World Wide Web
(c) Rajkumar
• 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.
10
Viewing WWW pages
(c) Rajkumar
View text, graphics, pictures, sounds, video
 Web Browser
 HyperText Markup Language (HTML)
 Computer Independent
 Operating System Independent

11
Web Browsers
(c) Rajkumar
Netscape Navigator
 Microsoft Internet Explorer
 Omni Web
 NCSA Mosaic
 Lynx (text only)

12
Internet
Organization
(c) Rajkumar
•Truly world-wide
•Multiple communication
media types
13
Internet Organization
(c) Rajkumar
Domains:
.edu
.org
.com
.mil
.biz
Computers:
fife.engr.vt.edu
www.engr.vt.edu
14
WWW Organization
(c) Rajkumar
Client
Client
Server
Server
Server
Client
Server
Client
Client
15
Generating Web Pages
(c) Rajkumar
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

16
HTML
(c) Rajkumar
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.

17
Internet Tools
(c) Rajkumar
• 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
18
How does the Web work ?
(c) Rajkumar
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

19
How does the Web Work
(c) Rajkumar
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
20
HTML document
(c) Rajkumar
<HTML>
<TITLE>Centre for Development of Advanced
Computing
</TITLE>
<BODY BGCOLOR=“#E7CCCC” TEXT=“#000000”
LINK=“#0000FF”>
...
...
<A HREF=“mailto:[email protected]>
webmaster</A>
</BODY>
</HTML>
21
(c) Rajkumar
22
URLs
(c) Rajkumar
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.ext:999/dir1/dir2/dir3/file.html?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

23
CGI (Common Gateway
Interface)
(c) Rajkumar
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

24
Authoring tools and Filters
(c) Rajkumar
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

25
Preconfigured v/s Integrated
Internet Products
(c) Rajkumar
Integrated Internet Products- From multiple vendors
 Preconfigured Systems- Web Server and a Client ready
to use
 Sun’s Netra Internet Server
 SGI’s WebFORCE Indy and WebFORCE Challenge S
 Apple’s Internet Server Solution
 DEC’s Internet AlphaServer
 Integraph’s Web Server 10

26
Future Directions
(c) Rajkumar
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

27
Internet in Education
(c) Rajkumar
* Creating Your Own Page
* Institution Web Site:
HTML Tags (Title, Body, images, etc.)
- about the university
Basic HTML code & file structure
- faculties and department details
Links and Anchors;
- research facilities, area, and groups
Linking it elsewhere:
- faculty members details with their publications
Moving around the WWW
* Admission Process:
Making it all Look ‘Pretty’
- course announcement,
- making available details of course
* Use components such as:
- admission applications,
- WWW Forms, Frames, Sound, Video,
- announcement of selection
- Animation, WWW Plugins
* University Facilities:
* Make web attractive through:
- computing facilities, accommodation, recreation, etc..
Adding web applications:
* Teaching Process:
- customer enquiry
- Use of WWW in the Curriculum
- Free applications
- Homework and Quizzes
- Virtual Classroom
- Virtual Lectures
- Student Interaction
-Q&A
28
Internet as a delivery Vehicle
(c) Rajkumar
29
Interesting URLs
(c) Rajkumar
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)
30

Class Sites To Visit
(c) Rajkumar
http://truth.phil.vt.edu/wwwcourses.html
 http://http://fiddle.visc.ece.vt.edu/courses/ee2504/
 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

31
API Bottleneck
(c) Rajkumar
MAC
PC
LAN
LAN
Server
SUN
Network
32
The OS - Platform lock
(c) Rajkumar
Applications tied to OS
Application
OS tied to Platform
OS
Application
Application
33
The Web
Application
(c) Rajkumar
* Seeded by HTML from CERN
* Revolutionised by MOSAIC
* Standardised, universal interface
to data
* Graphical
BROWSER
OS
Application
OS
OS OS
Application
* Broadcast capability publish once, reach millions
34
Making life easier!
(c) Rajkumar
 Data
on the web
 Browser platform independent
 Click on application - run on any
machine
 Java the programming language of
the 21 century
35
Java and Java Computing
(c) Rajkumar
36
Java - An Introduction
(c) Rajkumar
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++ -- ++ “

37
Java From 10,000 Ft.
(c) Rajkumar
According to the world, Java is...
 According to Sun, Java is...
 On closer inspection, Java is

38
According to the World,
Java Is...
(c) Rajkumar
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

39
According to Sun, Java is...
(c) Rajkumar
Simple and Powerful
 Object Oriented
 Portable
 Architecture Neutral
 Distributed
 Multi-threaded
 Robust, Secure/Safe
 Interpreted
 High Performance
 Dynamic pogramming language/platform.

Buzzword compliant!
40
On Closer Inspection, Java
is...
(c) Rajkumar
Simple
 Pure
 Portable
 Surprisingly effective

41
As a whole, Java is a Comprehensive
Programming Solution
(c) Rajkumar
Object Oriented
 Portable
 High Performance
 Geared for Distributed Environments
 Secure

42
Java as Object Oriented
(c) Rajkumar
“Objects all the way down”
 Simple and Familiar: “C++ Lite”
 No Pointers!
 Garbage Collector
 Dynamic Binding
 Single Inheritance with “Interfaces”

43
Java as Portable
(c) Rajkumar
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

44
Total Platform Independence
(c) Rajkumar
JAVA COMPILER
(translator)
JAVA BYTE CODE
(same for all platforms)
JAVA INTERPRETER
(one for each different system)
Windows 95
Macintosh
Solaris
Windows NT45
(c) Rajkumar
Java
Write Once, Run Anywhere
46
Architecture Neutral & Portable
(c) Rajkumar
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

47
Java as High Performance
(c) Rajkumar
JVM uses “lean and mean” bytecodes
 Small binary class filtes
 Just-in-time Compilers
 Multithreading
 Native Methods

48
Java in the World of
Distributed Computing
(c) Rajkumar
Class Loader
 Lightweight Binary Class Files
 Multithreading
 Dynamic
 Good communication constructs
 Secure

49
Java as Secure
(c) Rajkumar
Language designed as safe
 Strict compiler
 Dynamic Runtime Loading (Verifier)
 Runtime Security Manager

50
Object Oriented Languages
-a Comparison
(c) Rajkumar
Feature
Encapsulation
Inheritance
Multiple Inherit.
Polymorphism
Binding (Early/Late)
Concurrency
Garbage Collection
Genericity
Class Libraries
C++
Yes
Yes
Yes
Yes
Both
Poor
No
Yes
Yes
Objective
C
Ada
Java
Yes
Yes
Yes
Yes
Both
Poor
Yes
No
Yes
Yes
No
No
Yes
Early
Difficult
No
Yes
Limited
Yes
Yes
No
Yes
Late
Yes
Yes
No
Yes
51
Java better than C++ ?
(c) Rajkumar
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

52
Basic Data Types
(c) Rajkumar
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

53
(c) Rajkumar
Java Integrates
Power of Compiled Languages
and
Flexibility of Interpreted
Languages
54
Two Types of JavaApplications
(c) Rajkumar

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 <APPLET> tag. in html file)

55
Java Environment/
Life Cycle of Java Code
Runtime
Environment
(c) Rajkumar
Compile-time
Environment
Bytecode
Verifier
Java
Source
(.java)
Java
Compiler
Class
Loader
Java
Bytecodes
move locally
or through
network
Java
Interpreter
Just in
Time
Compiler
Java
Class
Libraries
Java
Virtual
machine
Runtime System
Java
Bytecode
(.class )
Operating System
Hardware
56
Java Development Kit
(c) Rajkumar
 javac
- The Java Compiler
 java - The Java Interpreter
 jdbThe 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

57
Hello Internet
(c) Rajkumar
// hello.java: Hello Internet program
class HelloInternet
{
public static void main(String args[])
{
System.out.println(“Hello Internet”);
}
}
58
Program Processing
(c) Rajkumar

Compilation
# javac hello.java
results in HelloInternet.class
 Execution
# java HelloInternet
Hello Internet
#
59
Simple Java Applet
(c) Rajkumar
// 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);
}
}
60
Calling an Applet
(c) Rajkumar
<HTML>
<TITLE> Hello Worls Applet </TITLE>
<APPLET code=“HelloWorld.class” width=500 height=500>
</APPLET>
</HTML>
61
Execution of Applets
(c) Rajkumar
1
APPLET
Development
“hello.java”
AT
CDAC-India
2
4
3
hello.class
AT C-DAC’S
WEB
SERVER
Create
Applet
tag in
HTML
document
Accessing
from
CRAY Corp.
(USA)
5
The browser
creates
a new
window and
a new thread
and
then runs the
code
Hello Java
<app=
“Hello”>
The Internet
Hello
62
Web Perspective
(c) Rajkumar
How did Web interactions work?
 How do they work with Java?
 Distributed Java objects and the Web

63
Classical Web Perspective
(c) Rajkumar
64
Java Web Perspective
(c) Rajkumar
65
Significance of
downloading Applets
(c) Rajkumar
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/StockDemo/standal
one.html
66
Power of Java and the Web
(c) Rajkumar
Deliver applications, not just information
 Eliminate porting
 Eliminate end-user installation
 Slash software distribution costs
 Reach millions of customers - instantly

67
Lifecycle of Java Code
(c) Rajkumar
68
Bytecode Verifier
(c) Rajkumar
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

69
Class Loader
(c) Rajkumar
Unique “Namespace” for each origin
 Local namespace classes are called “built-ins”
 Prevents class “spoofing”

70
Security Manager
(c) Rajkumar
Prevents unauthorized disk read/writes
 Restricts network access
 Other access restrictions (native methods)
 Implementation is browser dependent

71
General Language Features
(c) Rajkumar
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

72
Removed From C++
(c) Rajkumar
Operator overloading
 Pointers and Array/pointers
 Multiple-inheritance of implementation
 Enum, typedef, #define
 Copy constructors, destructors
 Templates
 And other stuff....

73
Added or Improved over C++
(c) Rajkumar
Interfaces: type Vs. class
 Garbage collection
 Exceptions (More powerful than C++)
 Strings
 Instanceof
 Package
 Multi-threads

74
Declaring Classes
(c) Rajkumar
class Queue {
Object data[];
Queue (int size) { // Constructor
data = new Object[size];
}
void add(Object o) {
// add to array in class specific manner...
}
// … other methods…
}
75
Inheritance in Java
(c) Rajkumar
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…
}
76
Creating and Using Objects
(c) Rajkumar
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...
77
Class Methods and Variables
(c) Rajkumar
 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);
78
Access Rules
(c) Rajkumar
 public
 private
 protected
 package
(Default - no keyword)
79
Using Threads
(c) Rajkumar
 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
80
Strings
(c) Rajkumar
The language defines strings as objects
 doSomething("abc" + "cde");
 doSomething(String s) { ..}
 String abc = new String(“Hello”);
 System.out.println(abc);

81
Exceptions
(c) Rajkumar
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

82
Exception Handling
(c) Rajkumar
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;
}
83
More about Exceptions
(c) Rajkumar
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
84
Interfaces
(c) Rajkumar
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{
..........}
85
Interface: Type and Sub-Type
(c) Rajkumar

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);
}
86
Class Implements Interface
(c) Rajkumar

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
87
Implementation Inheritance
(c) Rajkumar

Single inheritance of implementation
class X extends W implements E, F
{
// Stuff in class X
}
88
Interfaces and Classes!
(c) Rajkumar
89
Uses of Interfaces
(c) Rajkumar
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
90
Garbage Collected
(c) Rajkumar

No more manual memory management
class Recycler
{
public void recycle ()
{
Hashtable t;
for (int i=0; i<100; i++)
{
t = new Hashtable();
}
}
}

Significant elimination of programming bugs
91
instanceof and casts
(c) Rajkumar
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

92
Packages
(c) Rajkumar

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

93
Packages and Utilities
(c) Rajkumar
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)

94
Rich Object Environment
(c) Rajkumar
Core Classes
language
Utilities
Input/Output
Low-Level Networking
Abstract Graphical User Interface
 Internet Classes
TCP/IP Networking
WWW and HTML
Distributed Programs

95
Main Packages
(c) Rajkumar
 java.lang
 java.util
 java.io
 java.awt
 java.awt.image
 java.applet
 java.net
96
java.lang Core Classes
(c) Rajkumar
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);
97
java.lang Type Wrappers
(c) Rajkumar
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

98
java.io - Filtering input
streams
(c) Rajkumar
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());
}
99
(c) Rajkumar
GUI Programming in Java
(AWT and Event Handling)
100
AWT - Abstract Windowing
Toolkit
(c) Rajkumar
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

101
AWT - Abstract Window
Toolkit
(c) Rajkumar
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

102
Adding Components via
Layouts
(c) Rajkumar
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);
103
Adding Components via
Layouts
(c) Rajkumar
104
Popup Menu and Event Handling...
(c) Rajkumar
//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()
{
popup = new PopupMenu("Resource Usage" );
105
Popup Menu and Event Handling...
(c) Rajkumar
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() );
}
106
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();
}
(c) Rajkumar
}
107
Custom Drawing
(c) Rajkumar
// 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);
}
}
108
java.applet
(c) Rajkumar
Applet
 Class representation of applet
 init() method called when first loaded
 start() when applet’s 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

109
A sample Applet
(c) Rajkumar
// 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()
{
System.out.println("stop() method invoked");
}
}
110
(c) Rajkumar
Network/Socket Programming in Java
111
java.net
(c) Rajkumar

Used to manage:
 URL streams
 Client/server sockets
 Datagrams
112
Server side Socket Operations
(c) Rajkumar
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.getOutputStream() );
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.
}
113
Client side Socket Operations
(c) Rajkumar
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.getOutputStream() );
3. Perform communication with client
Receiive from client: String line = is.readLine();
Send to client: os.writeBytes("Hello\n");
4. Close sockets: client.close();
114
Echo Server Client..
(c) Rajkumar
//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 = args[0];
port_id = Integer.valueOf(args[1]).intValue();
try
{
slink = new Socket( server, port_id );
os = new DataOutputStream( slink.getOutputStream() );
is = new DataInputStream( slink.getInputStream() );
kbd = new DataInputStream( System.in );
}
115
Echo Server Client..
(c) Rajkumar
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 <end to stop>: ");
String line = kbd.readLine();
os.writeBytes( line+"\n" );
116
Echo Server Client..
if( line.equals("end") )
(c) Rajkumar {
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 < 2 )
{
System.out.println("Usage: java client server_name port_id" );
System.exit(1);
}
client cln = new client( args );
cln.communicate();
}
}
117
Echo Server ...
(c) Rajkumar
// 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 < 1 )
{
System.out.println( "Usage: java server port_num" );
System.exit( 1 );
}
int PORT = Integer.valueOf(args[0]).intValue();
try {
server = new ServerSocket( PORT );
}
118
Echo Server ...
(c) Rajkumar
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.getInetAddress();
System.out.println( "Client IP Addr: "+cip.toString());
is = new DataInputStream( client.getInputStream() );
os = new DataOutputStream( client.getOutputStream() );
for(;;)
{
String line = is.readLine();
if( line == null )
break;
119
Echo Server ...
(c) Rajkumar 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:"+args[0]);
}
}
}
120
Echo Server
System.out.println( "Server Down" );
(c) Rajkumar
try {
server.close();
} catch(IOException e) {}
}
}
121
(c) Rajkumar
Multithreading in Java
(A built-in feature in Java)
122
What are Threads?
(c) Rajkumar
 Thread is a piece of code that can execute in

concurrence with other threads.
It is a schedule entity on a processor
Hardware
Context
Registers
Status Word
Local state
Global/ shared state
PC
Hard/Software Context
Program Counter
Running
Thread Object
123
Single and Multithreaded
Processes
(c) Rajkumar
Single-threaded Process
Multiplethreaded Process
Threads of
Execution
Single instruction stream
Multiple instruction stream
Common
Address Space
124
OS:
Multi-Processing, Multi-Threaded
(c) Rajkumar
Threaded Libraries, Multi-threaded I/O
Application
Application
Application
Application
CPU
CPU
CPU
Better Response Times in
Multiple Application
Environments
CPU
CPU
CPU
Higher Throughput for
Parallelizeable Applications
125
Threaded Process Model
(c) Rajkumar
THREAD
STACK
SHARED
MEMORY
Threads within a process
THREAD
DATA
THREAD
TEXT
 Independent executables
 All threads are parts of a process hence communication
easier and simpler.
126
Levels of Parallelism:
Thread Granularity
(c) Rajkumar
Task i-l
 Task
 Control
 Data
 Multiple Issue
func1 ( )
{
....
....
}
a ( 0 ) =..
b ( 0 ) =..
+
Task i
func2 ( )
{
....
....
}
a ( 1 )=..
b ( 1 )=..
x
Task i+1
func3 ( )
{
....
....
}
a ( 2 )=..
b ( 2 )=..
Load
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
127
Multithreading - Uniprocessors
(c) Rajkumar

Concurrency Vs Parallelism
 Concurrency
P1
P2
CPU
P3
time
Number of Simulatneous execution units > no of CPUs
128
Multithreading Multiprocessors
(c) Rajkumar
Concurrency Vs Parallelism
CPU
P1
CPU
P2
CPU
P3
time
No of execution process = no of CPUs
129
Threads
(c) Rajkumar
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

130
Threading Mechanisms...
(c) Rajkumar 

Create a class that extends the Thread class
Create a class that implements the Runnable interface
131
1st method: Extending Thread class
(c) Rajkumar



1st Method: Extending the Thread class
class MyThread
{
public void
{
// thread
}
}
Creating thread:
MyThread thr1 =
Start Execution:
thr1.start();
extends Thread
run()
body of execution
new MyThread();
132
2nd method: Threads by implementing
Runnable interface
(c) Rajkumarclass
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();
133
Multi-Threaded
(c) Rajkumar
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()

134
Manipulation of Current Thread
// CurrentThreadDemo.java
(c) Rajkumar 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 i=5; i>0; i--) {
System.out.println(" " + i);
Thread.sleep(1000);
}
}
catch(InterruptedException e) {
System.out.println("Interrupted.");
}
}
}
Run:
Current Thread : Thread[My Thread,5,main]
5
4
3
2
1
135
Creating new Thread...
(c) Rajkumar // 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.");
}
136
...Creating new Thread.
(c) Rajkumar public void run()
{
try
{
for(int i=5; i>0; 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 : Thread[main,5,main]
5
4
3
Exiting main thread.
2
1
Exiting child thread.
}
137
Thread Priority...
(c) Rajkumar
// 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;
}
}
138
...Thread Priority
(c) Rajkumar
class HiLoPri
{
public static void main(String args[])
{
Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
Clicker Hi = new Clicker(Thread.NORM_PRIORITY+2);
Clicker Lo = new Clicker(Thread.NORM_PRIORITY-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)
304300 vs. 4066666
139
Threads Need Synchronization
(c) Rajkumar
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

140
Monitor model (for Syncronisation)
(c) Rajkumar
Method 1
Method 2
Key
Block 1
Threads
Monitor (synchronised) solves race-condition problem
141
Threads Synchronisation...
(c) Rajkumar
// 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;
new Thread(this).start();
}
142
...Threads Synchronisation.
public void run() {
(c) Rajkumar
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)
[Hello[Synchronized[World]
]
]
Run 2: With synchronized call method
[Hello]
[Synchronized]
[World]
Run3:Synchronized object in run(): synchronized(Target){ Target.call(msg); }
The output is the same as Run2
143
Queue (no inter-threaded communication)...
// pc.java: produce and consumer
(c) Rajkumar
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;
new Thread( this, "Producer").start();
}
144
Queue (no inter-threaded communication)...
(c) Rajkumar 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();
}
}
145
...Queue (no inter-threaded communication).
(c) Rajkumarclass 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
146
Queue (interthread communication)...
(c) Rajkumar// 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;
}
147
Queue (interthread communication)...
(c) Rajkumar
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;
new Thread( this, "Producer").start();
}
148
Queue (interthread communication)...
(c) Rajkumar
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();
}
}
149
...Queue (no interthread communication).
(c) Rajkumar 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
Got : 4
^C
150
Deadlock...
// DeadLock.java
(c) Rajkumar 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()
{
System.out.println("Inside A.last");
}
}
151
Deadlock...
class B
{
synchronized void bar(A a)
(c) Rajkumar
{
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()
{
System.out.println("Inside B.last");
}
}
152
...Deadlock.
class DeadLock implements Runnable {
(c) Rajkumar
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
Main Thread trying to call B.last()
Racing Thread trying to call A.last()
^C
153
Threads in Action...
Cooperative threads - File Copy
(c) Rajkumar
reader()
{
- - - - - - - - lock(buff[i]);
read(src,buff[i]);
unlock(buff[i]);
- - - - - - - - }
buff[0]
buff[1]
writer()
{
- - - - - - - - - lock(buff[i]);
write(src,buff[i]);
unlock(buff[i]);
- - - - - - - - - }
Cooperative Parallel Synchronized
Threads
154
Threads in Action...
Multithreaded Server
(c) Rajkumar
Server Process
Client Process
Server
Threads
Client Process
User Mode
Kernel Mode
Message Passing
Facility
155
A Look Inside the Java Platform
(c) Rajkumar
Applets and Applications
The
Java
Base
Platform
(in black)
Java Base API
Java Standard Extension API
Java Base Classes
Java Standard Extension Classes
Java Virtual Machine
Porting Interface
Adapter
Browser
OS
Hardware
Adapter
OS
Adapter
JavaOS
OS
Hardware
Hardware
Hardware
Java on a
Desktop OS
Java on a
Smaller OS
Java on
JavaOS
Network
Java on
a Browser
156
Java Applications!
(c) Rajkumar
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 ?

157
Universal Interface
(c) Rajkumar
Web Servers
with JAVA
applications
Internet
Clients
running
any OS on
any platform
158
Java on my platform ?
(c) Rajkumar
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.org:8001/projects/web/java/
 SGI http://liawww.epfl.ch/~simon/java/irixjdk.html
 HP http://www.gr.osf.org:8001/projects/web/java
 Linux http://www.blackdown.org
 AT & T
http://www.gr.osf.org:8001/projects/web/java
 Windows 3.1 http://www.alphaworks.ibm.com
159

(c) Rajkumar
Java Development Tools
(Present and Planned)
160
Sun’s Java WorkShop
(c) Rajkumar
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
161

Symantec Cafe 1.0
(Released)
(c) Rajkumar
Full IDE for Windows 95/NT
 Graphic Development Tools
 Two Compilers
 Debugger
 Class Browser

162
Microsoft Jakarta (Planned)
(c) Rajkumar
Visual C++ type interface
 Will Support ActiveX/COM
 Internet Explorer 3.0 will have Just-In-Time Java
compiler

163
Borland JBuilder
(c) Rajkumar
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 industrystandard 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
164

Challenges & Possible Directions
(c) Rajkumar
 Performance
 AWT
- need better GUI!
 Maintaining Interoperability
 Security - current restrictions limit what can
be done
 Native Compilers
 Is Portability that Important?
165
Comments
(c) Rajkumar
 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!
166
JDBC
(c) Rajkumar
Java API for Relational Databases
 Being standardized by all major players

167
Javascript and Java
(Preview)
(c) Rajkumar
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_Stuff()

168
Java for HPC!
(c) Rajkumar
Many efforts are in in progress for making java as a
language for parallel programming.
 Java computing frameworks (HPC, numeric, data
parallel)
 Java in distributed simulations and applications (e.g.,
real-world HPC, grand chalenge)
 Source to source translators (C, Fortran, C++ to Java)
 Web based computation environment in Java
 Java for HPC conference:
http://www.cs.ucsb.edu/conferences/java98
 Java for Science and Engineering computing:
subscribe java-for-cse to [email protected]
 http://www.jhpc.org
169

How to Convert Programs to AWT 1.1...
(c) Rajkumar
1. Change source code so that it import event
package:
import java.awt.event.*;
2. Figure out which component generates each
event type: (1.0 uses handleEvent() and action())
Button, List, MenuItem, TextField:
Interface: ActionListener
Method: actionPerformed(ActionEvent event)
Checkbox, CheckboxMenuItem, Choice:
Interface: ItemListener Method: itemStateChanged(..)
Dialog, Frame:
Interface: WindowListener
Method: windowClosing(), windowOpened(),...
170
How to Convert Programs to AWT 1.1...
(c) Rajkumar
3. Change class declaration so that class implements
public class MyClass extends SomeComponent
implements ActionListener
4. Register action Listener
newComponentObject.addActionListener(this);
5. Change event handling method:
Old: public boolean action(Event e, Object arg)
New: public void actionPerformed(ActionEvent e)
171
How to Convert Programs to AWT 1.1
(c) Rajkumar
6. Delete the event handling code in this way
(a) Delete all return statements
(b) Change e.target to e.getSource()
(c) Delete all code the unnecessarily tests for which
component the event come from
(d) Perform any other modification require to make
the program compile
172
Just to Summarize
(c) Rajkumar
 Java
as a Comprehensive Programming
Solution
 Object
Oriented
 Portable
 High Performance
 Geared for Distributed Environments
 Secure
 Highly suitable for Internet programming
173
Summary
(c) Rajkumar
Java is really very well poised
 Incredible leverage from the Web
 Will impact the C++ and Smalltalk markets
 Rate of progress is astonishingly high

Development environments
– CORBA linkages
– Components
–

Fasten you seat-belts!
174
The End
(c) Rajkumar
Questions
?
175
Thank You ...
(c) Rajkumar
?
176
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A Practical Guide to Java