Download Application Architecture Using Java

Application Architecture Using
Java
Hong Li
Introduction






Developed by a team led by James Gosling at Sun
Microsystem.
Originally called Oak, designed in 1991
Renamed Java in 1995, redesigned for developing
Internet Application
Full-featured, general-purpose programming
language
Java initially became attractive because Java
program can be run from a web browser. It is called
applet
Java can also be used to develop application on the
server side. Called Java servlets or JavaServer
Page
Characteristics of Java




Java is simple
Java is Object-Oriented
Java is distributed. Distributed computing
involves several computers working
together on a network.
Java is Interpreted. Programs are compiled
into the Java Virtual Machine code called
bytecode. The bytecode is machineindependent and can run on any machine
that has a Java interpreter, which is part of
the Java Virtual Machine (JVM)
Specification, API, JDK and
IDE


The Java language specification is a
technical definition of the language that
includes syntax and semantics
API contains predefined classes and
interfaces



J2SE-Java 2 standard edition
J2EE-Java 2 Enterprise Edition (server side
application)
J2ME-Java 2 Micro edition (mobile devices)
Java Development Toolkit
(JDK)


Sun releases each versions of J2SE with a Java
Development Toolkit (JDK)
JDK consists of a set of separate programs for
developing and testing Java program





Jbuilder by Borland (www.borland.com)
NetBean open source by Sun(www.netbeans.org)
Sun One, a comercial vrsion of NetBeans by Sun
Eclipse open source by IBM (www.eclipse.org)
These tools provide an integrated development
environment (IDE) for rapidly developing Java
programs.
Application and Applet



A Java program can be written in many
ways.
Applications are standalone programs.
It can be executed from any computer
with a Java interpreter
Applets are special kind of Java
programs that can run directly from a
Java-compatible Web Browser
A simple Java Program
Display message “Welcome to Java!”
// this application program prints Welcome to
Java!
// file name: Welcome.java
public class Welcome
{
public static void main(String [] args)
{
System.out.println(“Welcome to Java!”);
}
}

Class and methods



The class is essential Java construct. To program in
Java, you must understand classes and be able to
write and use them. A program is defined by using
one or more classes.
System.out is known as the standard output object.
println is a method in the object
Every Java application must have a user-declared
main method that defines where the program
begins. The Java interpreter executes the
application by invoking the main method
Displaying text in a message
dialog box









// file name: WelcomeDialog.java
import javax.swing.JoptionPane;
public class WelcomeDialog
{
public static void main(String[] args)
{
JOptionPane.showMessageDialog(null,
“Welcome to Java!”,”Example
2”,JOptionPane.INFORMATION_MESSAGE);
}
}
Jbuilder


Start->program->Jbuilder->Jbuilder
Creating project





File->new Project
Give a name and select directory, then click next
Keep all setting for path, then click next
For simplicity, uncheck Enable source package
discovery and compilation
Click finish
Jbuilder continued

Create a Java program File->new class



Compile a Java program


Give file name, check only public and generate
main method, uncheck others
Click OK
Project->make xxx.java
Execute a Java program

Run-> xxx.java using default