There are several important concepts in the J2ME platform, such as memory, CLDC, MIDP, etc. The beginner J2ME often understands these concepts, and even deviations. The purpose of this paper is to elaborate on the relevant important concepts in J2ME.
Memory We have been emphasizing that the memory of mobile information devices is very small, and it should be docplusted to use it, but we know how these memory is classified, and the following will be described in detail. In fact, the memory of the MIDP device is divided into three, Programme Memory, Heap, Persistent Storage. Programme Memory is a space assigned to MIDlet Suite because MIDlet suite is published in a JAR file, so the size of this file can be considered as the size of Program Memory. Some vendors are limited to the maximum value of Programme Memory. For example, my NOKIA 6108 is 64K, and if you exceed it, you will not be installed. Reduce the size of the MIDlet Suite is very important, a convenient method is to confuse the application using the obfuscator so that the size of the JAR file can be reduced. I will talk about how to use Proguard in future articles. HEAP is the storage space of the object that the application is stored during the run. The local variable and member variable are also placed on the HEAP, and the HEAP space provided in the MIDP device is approximately dozens of k to hundredsK. The space for the Persistent Storage is used to implement the local data persistence store for the MIDP application. In the Record Management System, I have done a detailed introduction in the entry into the proficiency.
2. Connected LIMITED Device Configuration
CLDC includes a Java virtual machine and a series of basic classes, J2ME's expert group gets their feature after hardware abstraction of mobile information devices, then designed and implemented Java virtual machines running on mobile information devices, usually we put It is called KVM. In CLDC 1.0, it also provides basic classes consisting of Java.io, Java.lang, Javax.microEditon.io, Java.util. Java.lang.Ref has been added in CLDC1.1.
3. Mobile Infomation Device Profile
MIDP is based on the CLDC, defined in the MIDP, and the application's lifecycle, user graphical interface, data management system, etc. are set, thus constructing a J2ME platform. Typically, the J2ME platform consists of a CLDC and one or more profiles.
For more detailed introduction to the J2ME platform, please refer to an article in IBM DeveloperWorks. Http://www-900.ibm.com/developerWorks/cn/java/l-j2metec/index.shtml
