Download No Slide Title

Introduction to JAVA
Explain the concept of Java as it
fits in the current development
environment.
Examine its basic components,
how it is implemented
Demo of Projects
1
GOALS...
To understand why Java is so
widely used
To identify Java’s benefits over
other languages
To identify the different type of
Java applications
2
There are many different
programming languages that
support different development
ideologies.
These ideologies have evolved
and were limited to the
hardware capabilities of the
time.
3
Initially, Computer programs
were written to merely automate
redundant clerical tasks.
4
However , with the development
of the PC and the World Wide
Web the thrust of application
development has been towards
more active, adaptive and
intelligent “systems” (data
mining , web surfing, decision
analysis)
5
COBOL, PASCAL, FORTRAN
Mainframe applications
Procedural
Extremely redundant, error
prone
NOT portable
Compiled into machine language
Need to be familiar with
platforms API
6
C
A “nuts and bolts” language
used for support systems (not
user interactive)
Multi platform development
(mainframe, unix, mac, pc)
7
C
Still extremely procedural,
redundant error prone
Somewhat portable (depends on
conformance to ANSI standards)
Lightweight
8
C
Compiled into machine language
Must know platform you are
developing in/for
Need to be familiar with
platforms API
9
C++
A “nuts and bolts” language
used for support systems (not
user interactive)
But has ability to develop GUI /
event driven apps (MFC)
Bulky to develop

10
C++
Many “versions”
Lightweight
Attempt to move from
procedural to OO
Does not enforce OO concepts
11
C++
Multi platform
Lends to redundancy and errors
Somewhat portable (depends on
conformance to ANSI standards)
Excellent for game development
12
C++
Compiled into machine language
Must know platform you are
developing in/for
Need to be familiar with
platforms API
13
Visual Basic, Powerbuilder
Mostly PC based
Easy IDE
Event Driven / GUI based
14
Visual Basic, Powerbuilder
Ideal for commercial application
development
Databases
15
Visual Basic, Powerbuilder
Introduces the ideas of
distributed processing Allows for
development of reusable
components
Run Time Interpreted
16
Visual Basic, Powerbuilder
Must know platform you are
developing in/for
Need to be familiar with
platforms API
17
What is Java ?:
Java is a language that:
was developed by Sun
Microsystems
18
What is Java ?:
Java is a language that:
was developed to take
advantage of (or enforce) the
principles of Object Oriented
Development
19
What is Java ?:
Java is a language that:
leverages the inherent benefits
of C++
utilizes C, C++ syntax
20
What is Java ?:
Java is a language that:
provides a standard Virtual
Machine (JVM) & Java Software
Development Kit (SDK)
enforces Object Oriented
development
21
What is Java ?:
Java is a language that:
lightweight (imports what is
needed, like C’s includes)
multi platform
greatly reduces redundancy
22
What is Java ?:
Java is a language that:
completely portable (go from pc
to unix to mac)
excellent for GUI, game, internet
development
23
What is Java ?:
Java is a language that:
compiled into Bytecodes, then
runtime interprited using the
JVM
Excellent Documentation --JAVADOC
24
What is Java ?:
Java is a language that:
Open Source
Do not need to know the specific
platforms API
25
What is Java ?:
Java is a language that:
Clean and consistent API
interface (actually abstracts the
developer from the specific API
of the platform on which the
program is being developed
26
What is Java ?:
Java is a language that:
This is how Java apps become
truly portable
Universal access to
documentation , tutorials, code
samples
27
What is Java ?:
Java is a language that:
Builds Applications
Builds Applets (executed via
Java enabled web browsers)
28
How Java works:
You need to download Java
Software Development Kit (SDK
or JDK) onto your PC
J2SDK 1.5.6 & Java 3D includes
a compiler, interpreter, applet
viewer program
29
How Java works:
You develop you Java program
using a simple notepad text
editor or using a more advanced
IDE like NetBeans, Eclipse,
Visual J++, Jcreator
30
How Java works:
You “compile” your program into
BYTECODE (close to machine
language, but abstracted from
any Specific machine code
instructions) Still platform
independent
31
How Java works:
When the program is executed,
the Java Virtual Machine
interprets your BYTECODE
BYTECODES are interpreted on a
particular computer by the Java
interpreter for THAT particular
CPU
32
How Java works:
Myapp.java source code
written in some text editor
(JAVA IS CaSE SenSITIvE)
Myjava.class compiled,
bytecode version of my program
Executed at runtime via JVM
33
How Java works:
Just In Time compilation One
time translation from byte code
to machine language
The next time that code is
executed, it is done from the
executable
34
How Java works:
This is why applets run much
faster the second time they are
“run”
35
Applets vs Applications:
Java applications are
constructed similar to C or C++
programs
They require a “MAIN” system
entry point (SPVM)
36
Java applications
They must all consist of classes
Every Java Class inherits from
Java.Lang.Object
37
Java applications
The name of the FILE that holds a
Java class MUST BE EXACTLY the
same as the name of that class
(CLASSNAME matches FILENAME)
This prevents having 2 runable
versions of the same class in the
same folder
38
Example:
the following code is from the
Sample project created in the
Intro to OO Lecture
HelloWorld.java
39
/*
* HelloWorld.java
* Java Application
* Description: Simple system output
display of “Hello World”
* @ author
David Farrell
* @ version 1.0
OUTPUT:
Hello World
*/
40
public class HelloWorld
{
public static void main(String[] args)
{
System.out.println(“Hello World”);
}
}
41
We will code and execute this
program in the next lecture (using
the NetBeans IDE) & examine the
code in detail in the Java
Application lecture
NOTE: the name of the java file
MATCHES the name of the class
(the class that contains SPVM)
42
Java Applets
have the same syntax as
applications
Have no “MAIN” entry point
Execute within Java enabled web
browsers
43
Java Applets
Uses the Java class JApplet
The name of the file MUST be
identical to the name of the
applets public class (less the .java
extension)
44
Java Applets
Applets auto Fire:
Init
Start
Paint
45
Example:
the following code is a the file
named
HelloWorld2.java
46
/*
* HelloWorld2.java
* Java Applet
* Description: Simple system output
display of “Hello World”
* @ author
David Farrell
* @ version 1.0
OUTPUT:
____________
Hello World
___________
*/
47
import javax.swing.Japplet
import java.awt.Graphics
public class HelloWorld2 extends JApplet
{
public void paint(Graphics g)
{
g.drawLine(15, 10, 210, 10);
// 15, 10 is x,y of st of ln 210, 10 x,y eol
g.drawLine(15, 30, 210, 30);
g.drawString(“Hello World”, 25. 25)
}
48
}
The HTML:
<html>
<applet code=”HelloWorld2.class”
width=300 height=40>
</applet>
</html>
49
Program Demos:
Craps Java Applet
CoinFlip2
Java Applet
DialogBoxForInput Java App (also
available in this lecture’s “Code
Sample” section
TicTacToe Java Applet ---- RUN
BY STARTING THE ASSOCIATED
index.html
50
Program Demos:
GO INTO
C:\Program
Files\Java\jdk1.5.0_06\demo\applets
Select a folder and CLICK on the HTML
to run the applets,
Open up and view the source code
51
Other Project Options:
GUI and Event Driven programs
possible:
Swing is like VB for creating Forms
with buttons, labels and textboxes
Graphics is like Open GL, SDL or
CMU graphics, Especially Java 3D
52
TEST IS NEXT !!!
53