【文章內(nèi)容簡介】 at can be implemented on small puting devices that have nonstandardhardware configurations. The Java Community Process Program has used a twofold approach to addressing the needs of small puting devices. First, they defined the Java runtime environment and core classes that operate on each device. This is referred to as the configuration. A configuration defines the Java Virtual Machine for a particular small puting device. There are two configurations, one for handheld devices and the other for plugin devices. Next, the Java Community Process Program defined a profile for categories of small puting devices. A profile consists of classes that enable developers to implement features found on a related group of small puting devices.6 J2ME configurationsThere are two configurations for J2ME as of this writing. These are Connected Limited Device Configuration (CLDC) and the Connected Device Configuration (CDC). The CLDC is designed for 16bit or 32bit small puting devices with limited amounts of memory.CLDC devices usually have between 160KB and 512KB of available memory and are battery powered. They also use an inconsistent, smallbandwidth network wirelessconnection and may not have a user interface. CLDC devices use the KJava VirtualMachine (KVM) implementation, which is a strippeddown version of the JVM. CLDCdevices include pagers, personal digital assistants, cell phones, dedicated terminals, andhandheld consumer devices with between 128KB and 512KB of memory.CDC devices use a 32bit architecture, have at least two megabytes of memoryavailable, and implement a plete functional JVM. CDC devices include digital settop boxes, home appliances, navigation systems, pointofsale terminals, and smart phones.7 J2ME ProfilesA profile consists of Java classes that enable implementation of features for either a particular small puting device or for a class of small puting devices. Small puting technology continues to evolve, and with that, there is an ongoing process of defining J2ME profiles. Seven profiles have been defined as of this writing. These are the Foundation Profile, Game Profile, Mobile Information Device Profile, PDA Profile, Personal Profile, Personal Basis Profile, and RMI Profile.■ The Foundation Profile is used with the CDC configuration and is the core for nearly all other profiles used with the CDC configuration because the Foundation Profile contains core Java classes.■ The Game Profile is also used with the CDC configuration and contains the necessary classes for developing game applications for any small puting device that uses the CDC configuration.■ The Mobile Information Device Profile (MIDP) is used with the CLDC configuration and contains classes that provide local storage, a user interface, and networking capabilities to an application that runs on a mobile puting device such as Palm OS devices. MIDP is used with wireless Java applications.■ The PDAProfile (PDAP) is used with the CLDC configuration and contains classes that utilize sophisticated resources found on personal digital assistants. These features include better displays and larger memory than similar resources found on MIDP mobile devices (such as cell phones).■ The Personal Profile is used with the CDC configuration and the Foundation Profile and contains classes to implement a plex user interface. The Foundation Profile provides core classes, and the Personal Profiles provide classes to implement a sophisticated user interface, which is a user interface that is capable of displaying multiple windows at a time.■ The Personal Basis Profile is similar to the Personal Profile in that it is used with the CDC configuration and the Foundation Profile. However, the Personal Basis Profile provides classes to implement a simple user interface, which is a user interface that is capable of displaying one window at a time.■ The RMI Profile is used with the CDC configuration and the Foundation Profile to provide Remote Method Invocation classes to the core classes contained in the Foundation Profile.There will likely be many profiles as the proliferation of small puting devices ontinues. Industry groups within the Java Community Process Program () define profiles. Each group establishes the standard rofile used by small puting devices manufactured by that industry.ACDC p