<p>I need to store large amount of data using RMS API through J2ME. </p>

<p>How can I store that multiple-column data, given they must be hardcoded so I need to store those multiple columns and rows data.</p>

<p>How can I do this in this, should I use <code>struct</code>s?</p>

Well, RMS only allows you to store records that are arrays of bytes. You will have to decide for yourself how a record is stored, and if you want to store your data in a single or in multiple records. If you use the DataInputStream and DataOutputStream classes, you'll be able to read/write Strings, booleans, integers, etc. The
API documentation includes a decent example
of how you can do this.
If you have complex data to store, or a lot of different objects, you may want to create a simple library for RMS I/O, that allows you to pass objects implementing e.g. "Storable" to a library class that writes away your object into RMS.