Symbian is an operating system for cell phones. Later versions of Symbian do support J2ME.

Windows Mobile is Microsoft's mobile solution. This platform is aimed at relatively high-end devices and developers with Windows expertise.

BREW is a C++ based framework that has support from Verizon. Developers for this platform can rely upon the phone carrier for billing and deployment. However, the certification process required for such support is an obstacle for small companies. IBM has built a JVM for BREW.

WAP is an excellent cell phone platform. Some form of it is supported on almost all modern phones; this is a strong selling point. The markup which sits on top of WAP 2.0 is XHTML.[6] Due to that fact, there is very little caching or data validation that can be done on the client.

J2ME is a Java based platform for cell phones. It includes everything needed to solve the traffic congestion service problem set: a GUI, persistent data storage, and network access. It is supported by a majority of cell phone carriers in the US, has no licensing issues, and is well documented.

CLDC stands for Connected Limited Device Configuration. In J2ME, a “configuration specification defines the minimum required complement of Java technology components and libraries for small connected devices”[8], including almost all of the supported classes in the java.lang package. Most cell phones will use this configuration. (There is another configuration, the Connected Device Configuration, for higher end devices.) At the time of writing, there are two versions of the CLDC: 1.0 and 1.1.

MIDP stands for Mobile Information Device Profile. This is a higher level API with which most developers will interact, and includes classes for the user interface, persistent data storage and other functionality.[9] Currently, there are two versions of this API: 1.0 and 2.0.

Optional packages are a crucial part of the J2ME platform, even though they seem to lack the requisite acronym. There is functionality that has been standardized by the JCP and that is a defined part of the J2ME platform: APIs such as JDBC, RMI and location based services (LBS). However, it may not be appropriate to have this functionality on every device. Therefore, it is not part of a profile or configuration, the implementation of which are mandatory. For example, if a device does not have the processor speed to support RMI marshalling and unmarshalling, the manufacturer may choose not to implement that package. But if they do, they must conform to the specification. Optional packages must be implemented by the phone manufacturer; they are not simple libraries that a developer can include with his midlet.

The J2ME platform on a given device consists of a device configuration (for example, CLDC) and a device profile (for example, MIDP), plus optional packages. In general, the configuration sits below the profile, and different versions of each may be paired. The configuration handles lower level interactions with the device, whereas the profile handles user interface and other higher level abstractions. Separating these allows them to evolve at different paces.

The J2ME API intersects with J2SE. Depending on the versions of the profile and configuration chosen, the java.io, java.lang, and java.util packages will be present (the red area below). In addition, there are some J2ME specific classes, in the javax.microedition package (the green area below). This package includes sub-packages which hold user interface, lifecycle, I/O and other J2ME specific classes.