Analysis of concepts of J2ME
J2ME, the Java 2 Micro Edition, is the SUN has introduced in mobile devices running on the Java platform, micro edition, mobile devices have a common cell phone, PDA, electronic dictionary, and a wide range of information terminals such as set-top boxes and so on.
As tens of thousands of mobile terminal types, but very large differences in computing power, not as simply as the desktop version of the JVM can be two or three to meet the Windows, Linux and Unix systems, therefore, J2ME is not a simple mini-version JVM. In order to meet the needs of mobile devices vary, SUN defines a series of specifications for different types of equipment, therefore, J2ME platform is composed of many of the standard set.
The most important of course, mobile phones, so we focused on J2ME mobile phone-related norms.
Configuration
SUN to different devices in accordance with the computing power into CLDC (Connected Limited Device Configuration) and CDC (Connected Device Configuration) two categories, both hardware and software environment for device Configuration is strictly defined, such as memory size is defined CLDC1.0 for the 64-512k, any device if the support CLDC1.0, we must strictly meet the definition, can not have optional or obscure features.
CLDC1.0 is very limited computing power for the device definition, only supports integer, floating-point operations are not supported, most of the early Java phone support CLDC1.0, such as the Nokia 3650, Siemens 6688i.
CLDC1.1 increase of floating-point operations, therefore, in support of CLDC1.1 device, you can use float and double types of variables. Many mobile phones can now support Java CLDC1.1, such as the Nokia 9500, Siemens S65.
CDC is more computing power for the definition of equipment, such as PPC, etc., CDC platforms and desktop JVM JVM is basically very close to, but you can use the Package substantially less than the J2SE package. Support the CDC's very high-end Java phones will be available shortly.
Profile
And Configuration comparison, Profile more of the software interface for the definition, Profile has to be achieved, there are optional features, therefore, Profile and more flexible.
Profile is of course the most important MIDP (Micro Information Device Profile), MIDP defines the Java mobile phones can run Java programs specification, including the application life cycle, various UI interface components to support Record Store and Http connections, etc. meet the standard MIDP Java applet is called MIDlet, you can download directly to your phone through a wireless network up and running.
Early MIDP1.0 specification enables us to run a UI in the mobile phone interface Java program, but MIDP1.0 support the game is not enough, must themselves achieve a number of code, so, MIDP2.0 specification greatly enhanced support for game development so that developers can write less code to create the game.
MIDP specification of the graphical interface are essentially independent of the AWT and Swing components J2SE, because the current computing power of mobile phones is still relatively limited, however, faster and faster as the phone's CPU, so AWT and Swing also migrate to mobile phones will be possible, therefore, based on CDC norms of the latest PBP 1.0 (Personal Basic Profile) and PP 1.0 (Personal Profile) provided some support for AWT and Swing, currently has some high-end PDA can run the Java program PBP and PP the. The foreseeable future, most of the AWT and Swing components can be ported to mobile phones.
As already mentioned, and compared to Configuration, Profile has a number of optional packages, more practical Profile are defined in JSR135 MMAPI (Mobile Media API), multimedia playback functions; defined in JSR184 M3G API (Mobile 3D Graphics API ), to achieve 3D function; defined in JSR120 WMA (Wireless Messageing API), to achieve short messaging. If your phone supports a Profile, such as M3G, it can be used in the MIDlet's 3D API M3G 3D games to achieve.
If you are ready to develop J2ME applications on the phone, choose phone makers need to pay attention to support the CLDC specification, supports MIDP1.0 or 2.0, whether to support the MMAPI, M3G, WMA and other optional packages.
Profile although the definition of the Java API interface, but how is the underlying decision by the vendors themselves, such as M3G defines a 3D interface, but the underlying implementation can either use the hardware acceleration can also be simulated by a C program, or in part by the hardware, some by the software.
More compact than the Java J2ME platform is SUN as JavaCard, run the credit card and other chips, the realization of electronic payment and other functions, not the current SUN JavaCard into the J2ME platform.
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