Java Mobile ProgrammingAfrica Nazarene University,Meru CampusMay Trimester, 2013Raphael Wanjiku,Computer Science Department
Introduction to Java Micro Edition (J2ME)This refers to Java for small devices. These range from pagers, mobile phones and PDAs.J2ME is classified into:a) Configurations: designed for specific kind of devices based on processing power andmemory. Device manufacturers are responsible for porting configurations into differentdevices. Configurations differ due to the device memory and processing power.Currently there are two configurations:i) Connected Device configuration (CDC) - has 512 ROM and 256 RAM.It is suited for set boxes, car-navigation systems and high-end PDAs.ii) Connected Limited Device Configuration (CLDC) - this includes mobilephones, PDAs, pagers and devices of similar size. These devices have limitedmemory, limited CPU power, limited display size, limited input and limited batterylife. It is based on a small JVM (Java Virtual Machine) called KVM.b) Profiles: layered on the configurations and provide additional APIs which enabledevelopment of applications of similar device family e.g. user interface, persistent storageand all that is required to run applications for the device.Mobile Information Device Profile (MIDP)This caters for a device with the following characteristics:i) A minimum memory of 256 Kb ROMii) A minimum of 256 Kb Java runtime available memoryiii) A screen of at least 96*54 pixels.iv) Some capacity for input, either keypad, keyboard or touch screen.
Advantages of MIDPa) Portability - An application written using MIDP API can run on any MIDP device.b) Security – Java is well known for its secure applets. A vital part of the bytecodeverification must be performed off the MIDP device. Secondly, CLDC does not allowapplication-defined class loaders.c) Additional APIs: these refer to anything else e.g. libraries that are required to enhancedevice capabilities, but for particular utility on the device. E.g. Bluetooth API