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What are several important concepts in J2ME programming? I believe many inexperienced people don't know what to do about it. Therefore, this paper summarizes the causes and solutions of the problem. Through this article, I hope you can solve this problem.

As we all know, Java ME, formerly known as J2ME (Java Platform,Micro Edition), is a Java language platform for embedded consumer electronic devices such as set-top boxes, mobile phones and PDA, including virtual machines and a series of standardized Java API. Together with Java SE and Java EE, it constitutes the three major versions of Java technology, and is also formulated through JCP (Java Community Process).

There are several important concepts in the J2ME platform, such as memory, CLDC, MIDP, etc. Beginners of J2ME often do not have a deep understanding of these concepts, or even have a deviation. The purpose of this paper is to elaborate on the related important concepts in J2ME.

1. Memory

We have always stressed that the memory of mobile information devices is very small and should be doubly treasured, but we rarely know how the memory is classified, which will be described in more detail below. In fact, there are three types of memory for MIDP devices, Programme Memory, Heap, and persistent Storage.

Programme Memory is the space allocated to MIDlet suite by mobile information devices, and because MIDlet suite is published as a jar file, the size of this file can be thought of as the size of Programme Memory. Some vendors have restrictions on the * value of Programme Memory. For example, the * value of my Nokia 6108 is 64k. If you exceed it, you will not be able to install it. Reducing the size of the MIDlet suite is very important, and a convenient way is to use an obfuscator to confuse the application, which can reduce the size of the jar file. I'll talk about how to use Proguard in a future article.

Heap is the storage space for the created objects in the running process of the application, and the local variables and member variables are also placed on the Heap. The Heap space provided in the MIDP device is about tens of k to hundreds of K.

The space of Persistent Storage is used to implement the local data persistence storage of MIDP applications, so I won't say any more about Record Management System from beginner to proficiency.

2. Connected Limited Device Configuration

CLDC includes a Java virtual machine and a series of basic classes. The expert group of J2ME abstracts their characteristics after abstracting the hardware of mobile information devices, and then designs and implements a java virtual machine running on mobile information devices, which is usually called KVM. CLDC1.0 also provides basic classes composed of java.io, java.lang, javax.microediton.io, and java.util. Java.lang.ref has been added to CLDC1.1.

3. Mobile Infomation Device Profile

MIDP runs on the basis of CLDC, and defines a subset of application life cycle, user graphical interface, data management system and so on in MIDP, thus building a J2ME platform. Typically, the J2ME platform consists of a CLDC and one or more Profile.

After reading the above, have you mastered the methods of several important concepts in J2ME programming? If you want to learn more skills or want to know more about it, you are welcome to follow the industry information channel, thank you for reading!

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