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Device programming with MIDP, Part 1

The concepts behind MIDP APIs and J2ME to build cross-<em>wireless</em>-platform apps

By Michael Cymerman, JavaWorld.com, 01/05/01

If you've been following the wireless industry, you've noticed the speed at which a technology runs through its life cycle. A brand new product can become obsolete within months due to an improved technology or platform. The result of that rapid change has been the lack of standardization between the deployment platforms in the wireless world. A development team currently needs its staff to understand numerous markup languages and processes in order to deploy a product onto multiple devices. A marketing department continually needs to modify product direction based on the changing marketplace.

Devices that are compliant with Mobile Information Device Profile (MIDP) will enable vendors to develop applications that can run on multiple wireless platforms without spending intensive amounts of energy customizing or reworking each platform. That would, in turn, let developers focus their energies on the system's functionality.

This article is the first in a three-part series designed to introduce you to the concept of MIDP APIs and the Java 2 Micro Edition (J2ME) platform. I will expose you to the APIs used to generate graphical, form-based, storage-driven code that can connect with external resources.

Introduction to J2ME

The J2ME is Sun Microsystems's attempt to port the Java programming language to devices with resource limitations. A mobile phone, which lacks the computational power, memory, and workstation power, cannot perform the same functionality as high-end servers or client workstations.

The J2ME platform is built upon the Java programming language to provide the maximum functionality available on the resource-limited device. A subset of the base functionality is provided along with some specialized classes.

In this article, I will focus on the CLDC (Connected Limited Device Configuration) and MIDP classes. Those sets of classes make up a profile in the J2ME terminology. That profile is based on the extremely limited device memory, processor speed, battery, and network connectivity bandwidth.

Introduction to CLDC APIs

The CLDC is the base platform on which the MIDP APIs are stacked. The CLDC classes consist of a standardized set of functionality that all vendors who offer J2ME-certified phones will support. Generally, you won't have to interact directly with those classes, but certain devices require that you access those lower-level classes to perform certain functionality. Those low-level accesses will likely be deprecated as the devices and platform develop.

Introduction to the MIDP profile

The MIDP profile has been developed to support the vertical niche of cell phones or similar devices constrained by screen and keypad limitations, in addition to the obvious battery, processor, and bandwidth constraints.

 

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