If you think it's a good idea to compress data as much as possible in order to save memory, think again, especially if you want to avoid slowing down your MIDlet.

3D model data used in a JSR-184 Java 3D MIDlet is typically stored in a file with an .m3g extension. JSR-184 allows some objects serialized in the file to be compressed. Since phone memory is always scarce, compressing data as much as possible seems to be a really good idea. But it's actually not. As a matter of fact, it's a really bad idea and just risks slowing down your MIDlet. This is because the .jar file that contains the .mg3 file is already compressed. Stated simply, compressing the data twice won't yield any benefits in terms of file size. And even worse, the handset spends additional processing time decompressing the objects in the .m3g file.

So, leave the objects in the .m3g file uncompressed.

*NOTE: At the time of writing this, there are no free tools for creating .m3g files available. However, as the JSR-184 market matures, many are on their way.