1. By Jeff Heaton http://www.jeffheaton.com
An Overview of J2ME
By Jeff Heaton

2. Using J2ME with Wireless Devices

3. Have a J2ME Cell Phone?

4. What is J2ME? Java2 Micro Edition
J2ME provides a platform for smaller devices, such as (from smaller to
Largest):
Pagers
Mobile Phones
PDA’s
Car Navigation Systems
Internet Appliances
Set-Top Boxes

5. The J2ME Universe

6. MIDP Mobile Information Device Profile
128KB of non-volatile memory for the MIDP implementation
32KB of volatile memory for the runtime heap
8KB of non-volatile memory for persistent data
Input capacity (screen, keyboard, touch)
Screen size of at least 96x54 pixels
Two-way network connection, possibly intermittent

7. MIDP vs J2SE No floating point (CLDC 1.0) No Object Finalization
No Reflection
No Native Methods
Threading, but no use of interrupt()
No file-based I/O
Many classes with fewer methods
Collections (Vector, Hashtable & Stack)

8. MIDP API (familiar packages)
java.io
java.lang
java.lang.ref
java.util

9. MIDP API (no so familiar packages)
javax.microedition.io
javax.microedition.lcdui
javax.microedition.lcdui.game
javax.microedition.media
javax.microedition.media.control
javax.microedition.midlet
javax.microedition.pki
javax.microedition.rms

10. What makes up a MIDP Application
MIDP Applications are composed of two principle parts
JAR File – Contains all of the classes and resources used by the application
JAD File – Application descriptor, describes how to run the MIDP application

11. JAD Files Very simple NON-XML config file Application Name
MIDI version
Copyright and version information
Location of the JAR file

12. Example JAD File
MIDlet-1: Jargoneer, Jargoneer.png, Jargoneer MIDlet-Jar-Size: 2369 MIDlet-Jar-URL: MIDlet-Name: Jargoneer MIDlet-Vendor: Unknown MIDlet-Version: 1.0 MicroEdition-Configuration: CLDC-1.0 MicroEdition-Profile: MIDP-1.0

13. Getting Started What do I need?
J2SE (
Sun’s J2ME Wireless Toolkit (
Internet Connection
Publicly accessible website or public static IP address

14. Example: Using KToolbar and a Emulator
Live demo.

15. Deploying MIDP
MIDP Applications are usually deployed Over the Air (OTA)
Using a HTTP web site
Can be distributed through vendor’s (i.e. Sprint) website (allows DRM)
Also can be distributed directly from any website (no DRM)

16. Sprint Security

17. Deploying MIDP via Web Server
Place your JAR and JAD files in a public HTTP folder.
For JAR files configure mime type: application/java-archive
For JAD files configure mime type: text/vnd.sun.j2me.app-descriptor
Point the cell phone at your JAD file: i.e.

18. Deploying from your computer
Install web server such as Apache
Determine your IP address
Setup mime-types
Open port 80 on your firewall, if your ISP allows you to use port 80
Use another port (i.e ) if your ISP does not allow port 80
Access your website with your cell phone

19. Things to Watch out For ISP and Cell Phone Caching Cryptic error codes
Mime-Types
Firewalls

20. Useful Web Resources
Midlet Error Codes
Deploy your J2ME Application
Sun Microsystems J2ME

21. Conclusion
Questions??