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Java 2 Platform, Micro Edition, or J2ME, is a collection of Java APIs targeting embedded consumer products such as PDAs, cell phones and other consumer appliances.
J2ME has become a popular option for creating games for cell phones, as they can be emulated on a PC during the development stage and easily uploaded to the phone. This contrasts with the difficulty of developing, testing, and loading games for other special gaming platforms such as those made by Nintendo, Sony, and others, as expensive system-specific hardware and kits are required.
Configurations and Profiles
J2ME devices implement a profile. The most common of these are the Mobile Information Device Profile aimed at mobile devices, such as cell phones, and the Personal Profile aimed at consumer products and embedded devices like Set-top boxes and PDAs.
A profile is a superset of a configuration, of which there are currently two: Connected Limited Device Configuration and Connected Device Configuration.
The CLDC contains a strict subset of the Java class libraries, and is the minimal needed for a Java virtual machine to operate.
Designed for cell phones, MIDP boasts an LCD-oriented GUI API, and MIDP 2.0 includes a basic 2D gaming API. Applications written for this profile are called MIDlets. Almost all new cell phones come with a MIDP implementation, and it is now the de facto standard for downloadable cell phone games.
The Information Module Profile (IMP) is a J2ME profile for embedded, "headless" devices such as vending machines, industrial embedded applications, security systems, and similar devices with either simple or no display and with some limited network connectivity.
Originally introduced by Siemens Mobile and Nokia as JSR-195, IMP 1.0 is a strict subset of MIDP 1.0 except that it doesn't include user interface APIs — in other words, it doesn't include support for the Java package javax.microedition.lcdui. JSR-228, also known as IMP-NG, is IMP's next generation that is based on MIDP 2.0, leveraging MIDP 2.0's new security and networking types and APIs, and other APIs such as PushRegistry and platformRequest(), but again it doesn't include UI APIs, nor the game API.
IMP applications are called IMlets, but in reality they are MIDlets. They subclass MIDlet, and follow the same packaging, deployment, security and life-cycle as MIDlets.
CDC is a larger subset of J2SE, containing almost all the libraries that are not GUI related.
Foundation Profile A headless version of J2SE.
Personal Basis Profile Extends the Foundation Profile to include lightweight GUI support in the form of an AWT subset.
Personal Profile This extension of Personal Basis Profile includes a more comprehensive AWT subset and adds applet support.
External links - The Source for J2ME Developers (J2ME Homepage) (http://java.sun.com/j2me)
- J2ME.org Forum (http://www.j2me.org)
- SprintDevelopers.com (http://www.sprintdevelopers.com) J2ME Programming for SprintPCS (Operator)
- developer.nextel.com J2ME Programming for Nextel (Operator)
- Micro Developer Network (http://www.microdevnet.com) Resource site for J2ME Developers with more industry related info.
- J2ME Polish (http://www.j2mepolish.org) Open Source Development Tool for J2ME
- j2me.ngphone.com/opensource J2ME Open Source Software Directory
- J2MEDeveloper.com (http://www.j2medeveloper.com) Resources for J2ME Developers
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