1. Topics on the presentation
JAVA is VM, development tools, language & packages
Networking
Embedded system & JAVA
License and cost
Author: Qi Wu

2. Applications on generic OS (Operating System)
Application 1 (ANSI C)
Application 2 (C++)
Application 3 (Pascal)
Application X (VB)
API (Application Programming Interface)
OS kernel
Software device drivers OS
Hardware interfaces
JAVA is VM, development tools, language & packages

3. Features of the architecture
API is much more dependent of an OS and/or selected hardware platform.
Applications are written in different programming languages and connected with certain API.
Performance/benchmark of an application is also affected by the OS and hardware platform.
What will happen if the OS or hardware platform changed ?
JAVA is VM, development tools, language & packages

4. Applications on generic OS (Operating System)
Application 1 (ANSI C)
Application 2 (C++)
Application 3 (Pascal)
Application X (VB)
To be updated
API (Application Programming Interface)
OS kernel
Software device drivers OS
Hardware interfaces
JAVA is VM, development tools, language & packages

5. JAVA is VM, development tools, language & packages
Portability
Selection of a OS or hardware platform is often requirement from big customer.
Update of existing applications needs additional efforts and time.
Maintain of applications becomes problem.
JAVA is VM, development tools, language & packages

6. JAVA VM (Virtual Machine)
Application 1 (JAVA)
Application 2 (JAVA)
Application 3 (JAVA)
Application X (JAVA)
JAVA byte code
JAVA VM
Packages
API (Application Programming Interface)
OS kernel
Software device drivers
Hardware interfaces
JAVA specifications
VM producer’s job
JAVA is VM, development tools, language & packages

7. Features of the architecture
VM is upward standard according to JAVA specification and downward specific to an OS
Business strategy drives producer of an OS to release JAVA VM in some case. Some communities are also working hard on JAVA VM for different OS like Windows 95/98/NT/2000, Window CE, Linux, QNX...
Application is written once and run everywhere (theoretically). More and more applications are written in JAVA and treated to be independent of certain OS.
Performance/benchmark of an application is also affected by the OS, hardware platform and JAVA VM.
Packages are collection of specified or often-used classes. Standard JAVA specification defines rich classes for diverse applications.
JAVA is VM, development tools, language & packages

8. java.net.* and java.awt.* are important packages
Application 1 (JAVA)
Application 2 (JAVA)
Application 3 (JAVA)
Application X (JAVA)
JAVA byte code
JAVA VM
Packages
(java.net.*
java.awt.*
...)
API
TCP/IP
GUI
OS kernel
Software device drivers
Hardware interfaces
JAVA specifications
VM producer’s job
JAVA is VM, development tools, language & packages

9. JDK (Java Development Kit)
JAVA is VM, development tools, language & packages

10. Sub-directories of JAVA 1.3 (Java 2) based on Sun’s Standard Edition
JDK 1.3 root directory
bin
include
demo
lib
jre
javac.exe --- compiler
jdb.exe debugger
java.exe Java VM
appletviewer.exe
....
src.jar --- packages
....
JAVA is VM, development tools, language & packages

11. JAVA is VM, development tools, language & packages
Example 1: Welcome.java
public class Welcome
{ public static void main(String[ ] args)
{ String greeting[ ] = new String[3];
greeting[0] = “Welcome to Hannover”;
greeting[1] = “by Qi Wu”;
greeting[2] = “on April 08, 2001”;
for (int i = 0; i < greeting.length; ++i)
System.out.println(greeting[i]); }
JAVA is VM, development tools, language & packages

12. JAVA is VM, development tools, language & packages
Example 1: Welcome.java
C:\JAVATEST>javac Welcome.java
C:\JAVATEST>java Welcome.class
...
Welcome to Hannover
by Qi Wu
on April 08, 2001
C:\JAVATEST>_
JAVA is VM, development tools, language & packages

13. Features of Java language
The concept of class dominates all Java
Java is OOP
Garbage collection
Java Interface
Easy to design, code and test
Most data exchanges are based on reference
...
JAVA is VM, development tools, language & packages

14. JAVA is VM, development tools, language & packages
Example 2: Welcome.java
public class NewWelcome {
public String getLine(String strArray[ ]) {
return strArray[ 0] + “ “+ strArray[ 1] + “ “+ strArray[ 2]; }
public class Welcome
public Welcome {
NewWelcome myNewWelcomeObject = new NewWelcome();
System.out.println( myNewWelcomeObject.getLine(greeting) );
public static void main(String[ ] args)
{ String greeting[ ] = new String[3];
greeting[0] = “Welcome to Hannover”;
greeting[1] = “by Qi Wu”;
greeting[2] = “on April 08, 2001”;
Welcome myWelcomeObject = new Welcome();
JAVA is VM, development tools, language & packages

15. JAVA is VM, development tools, language & packages
What is class?
A class is usually described as the template or blueprint from
which the object is actually made.
JAVA is VM, development tools, language & packages

16. Networking buzzwords Networking Internet EJB Intranet http Servlet
socket
Applet
Client/server
...
TCP/IP
Networking

17. Generic & basic networking layer structure
Application Protocol (http, ...)
TCP/UDP/IP
Abstract layer
Physical link
Hardware interfaces
Networking

18. Java networking solution Application Protocol (http, ...)
JAVA VM
Application Protocol (http, ...)
Packages
(java.net.*
...)
TCP/UDP/IP
JAVA specifications
Networking

19. Client/server concept (two or more machines) Pooling & response thread
TCP/UDP/IP
Application Protocol (http, ...)
JAVA VM
Request thread
TCP/UDP/IP
Application Protocol (http, ...)
JAVA VM
Server
Networking

20. Client/server concept (two o more machines) Pooling & response thread
TCP/UDP/IP
Application Protocol (http, ...)
JAVA VM
Request thread
Application Protocol (http, ...)
TCP/UDP/IP
Server
Networking

21. Client/server concept (one machine) Pooling & response thread
Request thread
TCP/UDP/IP
Application Protocol (http, ...)
JAVA VM
Networking

22. Client/server concept (one machine)
Pooling & response thread
Request thread
JAVA VM
Application Protocol (http, ...)
TCP/UDP/IP
Networking