Generally, it’s a bad idea to use RIM API calls when you are writing a J2ME application for Blackberry. Here are some research items covering this topic:
RIM Development: Fundamentals
RIM DOCS: Web page for general RIM documentation.
RIM MIDlets: Creating a MIDlet
RIM and J2ME: Advantages and Disadvantages
RIM MIDlet Development Guide: The Official RIM MIDlet Dev Guide.
ARTICLE: Programming J2ME on RIM