Thread: How to start writing Java Apps for Cell Phones?

Hello Jchang504,

I have moved this thread over to our Java ME forum.

This is because cell phone applications are written with Java Micro Edition.

Java Platform, Micro Edition (Java ME) provides a robust, flexible environment for applications running on mobile and other embedded devices—mobile phones, personal digital assistants (PDAs), TV set-top boxes, and printers. Java ME includes flexible user interfaces, robust security, built-in network protocols, and support for networked and offline applications that can be downloaded dynamically. Applications based on Java ME are portable across many devices, yet leverage each device's native capabilities.

I suggest you read through these 2 links. They will give you all the information you need to know!

Java ME - the Most Ubiquitous Application Platform for Mobile Devices

Java Platform, Micro Edition - Wikipedia, the free encyclopedia

Nearly all cell phones will run Java applications now days. You don't need a special type of phone or any complex knowledge on how the phone works.

Good luck

Hello Jchang504,

Yes you can write these applications like you would normally but you will need to have a emulator which emulates the application working on a mobile environment.

You can download the Sun Wireless Toolkit for this. Check these:

Java ME Emulator Toolkits

Java ME Technology APIs & Docs

All mobile phones come with a computer cable or bluetooth which will allow them to be connected to the computer. You can upload and run .jar files on mobile phones.

I have limited knowledge of Java ME but I suggest you download the wireless toolkit and read the documentation

Originally Posted by Jchang504

I downloaded the Java ME SDK 3.0 from here: Download Java Platform Micro Edition Software Development Kit 3.0
Is that the right thing to download?

And if you say .jar files run on a mobile phone, that means I can load in some of the programs I have already packaged as .jar 's that I use on my computer?

Hello Jchang504.

Yes this is the correct IDE to download. It looks like it contains everything you need to get started including the mobile emulation.

You cannot run your normal applications on a mobile as a .jar. Your .jar need to contain J2ME Midlets.

Traditionally, Java downloadable packages have been called applets. For J2ME, however, these downloadable packages are referred to as midlets, as they are written for the Mobile Information Device Profile - or MIDP - which is specifically designed for the constraints of a mobile phone. So, when you download 'Java', you're downloading a Java midlet.

It's the midlets that contain the Java code that make the thing you downloaded actually do something. The great thing about Java is that you really don't need to know anything about how it all works in order to use it. All the code that's part of a midlet is contained in something called a JAR file (short for Java ARchive file, and identified by its file extension .jar), which is basically just a zip file that keeps all the files and classes specific to that midlet together. This means you need only worry about one file - the .jar file - irrespective of how complex the code contained within that file's classes is. It's the .jar file that you download onto your PC, upload onto your phone from your PC, or transfer onto your phone over the air via WAP.

Please read this tutorial:

HowTo: Install Java J2ME midlets on your mobile phone