Chapter 2 connecting limited device configuration (cldc) 2.1

Configure a connection device(Cldc)YesJ2EEFor small devices such as cell phones,PagersAnd low-endPDACreate the basic component of the Summary. These devices are characterized by limited storage and processing capabilities, which makes it impossible for them to carryJavaAll features of the platform.CldcDevelopedJavaMinimum set of packages and classes and a function for downgradingJavaVirtual machine, so that you can run in an environment with limited resourcesJavaApplication.

The first part of this chapter describes the supportedCldcOfJavaA virtual machine must provide features that explain the differences between the virtual machine and the Standard Virtual Machine. As part of this discussion, we will useSunOfCldcReference implementation andKilobyteVirtual Machine (KVM,). The second part introducesCldcThe packages and classes required for implementation areJ2seA subset of the core package. This chapterKVMThe discussion of the provided debugging functions and some advanced features are completed using the native code and PreloadJavaClass --Source codeLevel-of-useKVMReaders are valuable.

2.1 cldc JavaVirtual Machine

Hardware and software restrictionsCldcThe device is not supported.J2seAll core classes. InWindowsEasy to run on the platform'Hello, world"Probably16 MB. Compared with this,CldcThe minimum platform requirements are:

Ü128kbOfRom,Flash memory or battery memory for permanent storageJavaVirtual Machine and buildCldcThe required class library.

Ü32kbMemory is easy to lose for allocation at runtime. This memory is satisfiedJavaDynamic Requirements of applications, including class loading, object heap space, and stack allocation

To be supported in such a restricted environmentJavaRunning environment,CldcVirtual machines, languages, and core class libraries are defined to narrow down requirements. They are described in the following sections.

CldcThere are few assumptions about its main platform, rather than storage requirements. For example, it does not assume that the device will have any form of display and input devices such as the keyboard and mouse, and it does not need to store any form of local application data. These problems are assumed to be provided by their respective manufacturers. Of course,J2EEThere are additional requirements for limited devices, as you will do in Chapter 3 and chapter 7. ForCldcThe demand is minimized to maximize the number of platforms that can be achieved.

When the software environment is created,CldcAssume that the master device has an operating system to execute and manage virtual machines. AlthoughJavaIs a multi-threaded programming environment, the operating system does not necessarily need the concept of a thread or the ability to run multiple processes at any time. On the contrary, virtual machines must be able to use local functions to provide multi-threaded environment simulation.

CldcByJCPDeveloped on the following sites:Http://jcp.org/jsr/detail/30.jsp