J2ME By Example, How to enter Mobile World

We will start in this series simple easy tutorials to start from zero in J2ME track, so stay with us.


1)J2ME Architecture

There are 5 layers in J2ME Architecture.Those are:

• MIDP (TopMost Layer): Which contains Java APIs for user network connections, persistence storage, and the user interface. It also has access to CLDC libraries and MIDP libraries.
• J2ME API’s(Profiles): Which consists of the minimum set of application programming interfaces for the small computing device
• Configurations: Which handles interactions between the profile and the JVM.
• JVM
• Operating System(Bottom Layer).

2)Simple Example Program

This section shows a simple application. The MIDlet will display the message “ Hi This is My First Program” on the screen. The application consists of the MIDlet subclass called welcome.

To create midlet .

Right-click on project name --> new --> MIDlet

The code .

The run of the project

3) Limitations with J2ME

Some of the limitations of J2ME compared with Core JAVA

• Some J2SE applications require classes that are not available in J2ME.
• Java applications won’t run in the J2ME environment without requiring modification to the code.
• Devices that use the CDC configuration use the full Java Virtual Machine implementation, while devices that use the CLDC configuration use the Kjava Virtual Machine implementation.
• MIDlets are controlled by application management software (AMS). So we cant invoke a MIDLET like a J2SE Application.

4)Conclusion

Here with we have an introduction to Java 2 Micro Edition. This example is very simple example. It can be executed using editors like NetBeans IDE or J2ME Wireless Toolkit(KToolBar). Using API's like JSR 135 etc.. try to create more programs and try them in these tools. I will get back to you with more articles on J2ME.

Project Source Code : Click Here

Disclaimer:

This Tutorial written by Ahmed Shoeib.So Many thanks for his support, we hope to enjoy his awesome posts.