Because J2ME is designed for small devices with limited memory, much of the usual Java preverification has been removed from the virtual machine to allow for a smaller footprint. As a result, it is necessary to preverify your J2ME application before deployment. An additional check is made at run time to make sure that the class has not changed since preverification.
Exactly how to perform the preverification, or checking the classes for correctness, depends on the toolkit. CLDC comes with a command-line utility called preverify, which does the actual verification and inserts extra information into the class files. MIDP uses the wireless toolkit, which comes with a GUI tool, though this too can be run from the command line.
Deployment depends on the platform to which you are deploying. The application must be packaged and deployed in a format suitable for the type of J2ME device, as defined by the profile.