In 2004, mobile development was probably the most fashionable word. In a recent survey, 24.34% of respondents involved in embedded / mobile device applications, this number may be slightly higher than the actual proportion, but it is also possible to explain that embedded / mobile device application development is a tempting Fresh cheese. J2ME is the king of embedded / mobile application platform, Linux, and WinCe listing two and three. The Symbian platform for NOKIA and other vendors currently developer share has not yet fulfilled satisfactory levels, considering that the survey combines embedded devices (such as PDA) and mobile devices (such as smartphones), Symbian, WinCE series will be on the mobile platform. The main two parties of competition. If the manufacturer can do more norms in standard implementation, J2ME's cross-platform feature will play more dripping, continue to keep the king's status. J2ME is a development platform for SUNs to embedded consumer electronics, which integrates three important branches of Java technology with J2SE and J2EE. J2ME is actually a collection of specifications, which is implemented by JCP organizations and releases, and individual vendors will be implemented on their own products in accordance with specifications, but they must be tested through TCK to ensure compatibility. For example, the MIDP2.0 specification is in JSR118. The J2ME platform has been quite a taste of Java technology to return. We know that Java is originally a programming language for consumer electronics, and then slowly develop into a technology, one platform. Talking about J2ME We usually speak a word KVM, and this can be considered J2ME's origin, KVM's father Antero TAIVALSAARI is participating in a research-based project called Spotless, because he has manufactured in world-renowned telecom equipment manufacturing The experience of business, this makes him germination of the idea of mobile terminal equipment, such as mobile phones, and implementing Java virtual machines, and this is supported by the manager. Then AT as a leader who led the team to develop virtual machines and CLDC core libraries that can run on mobile terminals such as mobile phones. Slowly J2ME floats the water. J2ME design should be said to be a number of top engineers cry, she is designed very flexible. The two concepts in J2ME are Configuration and Profile. Configuration is the smallest platform that supports the maximum range of devices, and also includes Java virtual machines at this layer. Profile provides a corresponding development package collection for specific devices. In addition to certain features, J2ME also introduces the concept of Optional Profile. For example, Mobile Media API.
There are two main Configuration in the J2ME platform, one is Connected Limited Device Configuration, one is Connected Device Configuration. The standardization of distinguishing is the hardware characteristics such as processors, memory, networked capabilities. Since these specifications have been made early, the current mobile terminal equipment has a qualitative leap. So no longer list the standards of distinguishing, because that is no meaning, you will even think that it is wrong. At present, the application of J2ME is mainly based on CLDC, so this article will mainly introduce the reader to the J2ME platform based on CLDC. However, the author's development project in two world famous telecommunications equipment demonstrates that CDC-based applications will slowly occupy the mainstream market, as CDC provides more powerful class library support. Onformation Device Profile is located on CLDC, and there is no extensive attention to developers after the CLDC specification is set, and there is no change in the market. The reason is that the CLDC does not provide an interface for graphical user interface programming, so that the application does not have the ability to interact with the user. The launch of MIDP1.0 has been widely concerned by developers. A new application model MIDLET is proposed in MIDP 1.0. Developers can also develop graphical user interface programs in the Javax.microedtion.lcdui package provided in MIDP. Data's persistence operations with MIDP1.0 subsystem Record Management System, using the network capabilities of the Generic Connection Framework provided in CLDC access to the web server via HTTP protocol, and J2ME is almost omnipos. However, some problems are slowly exposed. Since the MIDP's norms have become too broad, the function is limited, resulting in a lot of differences in functional characteristics in various vendors, such as the size of the application, RMS storage space, The number of threads in parallel, etc. Worse, various manufacturers have implemented a number of functions outside J2ME, such as the function of sound processing and full screen in the NOKIA UI API, which destroys the Java cross-platform feature, if you have a NOKIA UI API in your program Then it can't be ported to Motorola's mobile phone device. To make up these shortcomings, Sun launched a subset of MMAPI in subsequent MIDP2.0 to solve the shortcomings of sound processing, and designed a separate game development package javax.microedition.lcdui.game for game development, Push, Socket networking and other features provide support. In JSR185, Java Technology for the Wireless Industry is more stringent in Java Technology, which improves the compatibility of the application. Not only that, the optional packages in J2ME are more powerful, Blowtooth API, SIP API for J2ME and Mobile 3D Graphics provide very powerful features. J2ME's development and competitive software environment rapidly develop, the hardware environment and market of J2ME platforms is equally mature. The number of Java mobile phones is growing, and the number of Java mobile phones is expected to exceed 600 million in 2006. Accelerated integrated Java in hardware is expected to further promote the popularity of Java in the market, J2ME will become in fact standard. By 2006, Java mobile phones are expected to account for 83% of all mobile phone shipments. At the same time, the transition of the mobile value-added business has greatly promoted the development of J2ME technology, which is expected to reach 14.7 billion US dollars by the Global Value-added business market in 2008. In 2004, Microsoft began to gradually enter the mobile communication industry, and launched a built-in Microsoft Smartphone mobile phone with US telecommunications equipment manufacturers in the United States. Other Qualcomm's BREW and NOKIA Symbian have always considered J2ME competitors.
