Mobile Information Device Profile (MIDP) is a specification published for the use of Java on embedded devices such as mobile phones and PDAs. MIDP is part of the Java Platform, Micro Edition (Java ME) framework and sits on top of Connected Limited Device Configuration, a set of lower level programming interfaces. MIDP was developed under the Java Community Process as JSR 37 (MIDP 1.0) and JSR 118 (MIDP 2.0). As of 2007, MIDP 3.0 is being developed under JSR 271. The first MIDP devices were models i80s and i50sx from Motorola, launched in April 2001.

Noteworthy Limitations of MIDP 1.0

• MIDP 1.0 has no active rendering APIs
• MIDP 1.0 has no support for direct access to image pixels (RGB data)
• MIDP 1.0 has no support for full screen mode
• MIDP 1.0 has no support for audio.
• MIDP 1.0 requires only HTTP support.
• MIDP 1.0 cannot query key status (although key events are supported)
• The specifications are not always clear, leading to differences in implementations.
• Some limitations may be avoided by using a vendor-specific API or MIDP 2.0, which obviously reduces the portability of the application.

General APIs

The core APIs are defined by the underlying Connected Limited Device Configuration.

javax.microedition.io

Contains the Java ME-specific classes used for I/O operations.

javax.microedition.lcdui

Contains the Java ME-specific classes used for the GUI.

LCDUI has a simple screen based approach where a single Displayable is always active at a time in the application user interface. LCDUI API provides a small set of displayables common in mobile device user interfaces: List, Alert, TextBox, Form and Canvas. For all displayables the device MIDP implementation has control over the presentation and layout of the displayable. Canvas is a low-level graphics surface for which an application has full control over what is rendered to it, although normally some space is reserved for system areas like screen title and indicators common in mobile device UIs. Since MIDP 2.0, Canvas also supports a full-screen mode that allows to make full screen graphics, which is especially useful for games.

LCDUI also has quite unique approach of abstract operations, called Commands. The placement of commands added to a displayable is completely up to the device implementation of this toolkit. The application programmer uses API specified command types to indicate the usage or purpose of the command in application user interface. Common types are BACK, EXIT, ITEM, SCREEN. The idea of the command abstraction is to make applications more portable between various different mobile device. Application developers should use the command types properly to indicate the purpose of an operation, and device implementation then places the operation to the common location for a given type in device's specific user interface style. This may be e.g. a specific key, like "a back navigation key" for BACK commands or button on screen.