From Forum Nokia Wiki

In order to avoid the some of the draw backs of the MIDP 1.0 implementation, Nokia has added a proprietary API to phones mainly in the UI category. For making user-friendly games/applications great Java support is required in the low-level API which is not given by the MIDP 1.0 criteria.

Almost all the specifications in Nokia UI is supported in MIDP 2.0, so using Nokia UI API is not recommended for MIDP 2.0 for the future concern that the applications may have to be ported to other vendor devices.

Main areas of this Nokia UI API are Sound & Full Canvas.

Following things of Nokia UI API are still missing from MIDP 2.0 APIs:

• Transparent or semi-transparent drawing targets (mutable off-screen images with alpha channel)
• Alpha channel support in graphics drawing primitives
• Fine grain control over device backlight (turning backlight on for a period of time).

These provide very interesting use cases that still are impossible via standard APIs like MIDP 2.0. For example, in many applications it's important to keep the backlight on without user need to press keys. Examples applications include Mobile TV or video viewers, navigation/map applications, turn based games like chess etc.

The low-level graphics transparency features allow to create modern UI effects.

A number of Sony Ericsson phones (Java Platforms, JP, 3-8) also support Nokia UI API. This has made it easy to port games/applications using Nokia UI API to Sony Ericsson phones as well.

Nokia UI API Specification

• http://www.forum.nokia.com/main/resources/technologies/java/documentation/java_jsr.html#ui
• http://java2me.org/NokiaUI/doc/index.html

Phones supporting Nokia UI API http://www.j2mepolish.org/devices/devices-nokia-ui.html