J2ME in a Nutshell

Chapter 6. Wireless Java: Networking and Persistent Storage

The devices that the J2ME platform is intended for are, by their nature, reliant for their usefulness on the ability to communicate with the outside world. Cell phones, of course, serve no real purpose other than to exist on a network, while PDAs would be much less useful if you could not connect them occasionally to a desktop computer to save your new customer orders or upload more appointments from your departmental calendar. As important as networking is, however, there is a certain cost to be paid for it in terms of the resources needed for the software that implements the various networking protocols in use today. Given the relatively small amount of memory and processing power available in cell phones and the smaller PDAs, compromises have to be made in order to provide networking support for the type of hardware on which profiles designed for the CLDC are run. The same constraints do not exist for the larger devices that host CDC profiles. Not surprisingly, then, these two different profile families incorporate completely different communication software architectures. This chapter looks at networking and communications in the context of the CLDC configuration and MIDP, which differs greatly from its CDC equivalent, covered in Chapter 7.

This chapter also looks at another essential feature for a mobile device: the ability to store information and access it from applications running on that device. The type of storage ...