1Basics of J2ME

2 Objectives –Understand the different java API’s and how the mobile edition API’s fit in –Understand what a mobile configuration and profile is.

3Basics of J2ME Basics of J2ME showing various editions Java 2 Enterprise Edition (J2EE) Java 2 Standard Edition (J2SE) Java Virtual Machine CDCCLDC MIDPProfile Level Configuration Level KVM Java 2 Micro Edition (J2ME)

4 The Java Platform Basics of J2ME

5 Configurations “Configurations comprise a virtual machine and a minimal set of class libraries. They provide the base functionality for a particular range of devices that share similar characteristics, such as network connectivity and memory footprint. Currently, there are two J2ME configurations: the Connected Limited Device Configuration (CLDC) and the Connected Device Configuration (CDC). “

6Basics of J2ME Configurations Connected Device Configuration (CDC) –512 kilobytes (minimum) memory for running Java –256 kilobytes (minimum) for runtime memory allocation –Network connectivity, possibly persistent and high bandwidth Connected, Limited Device Configuration (CLDC) –128 kilobytes memory for running Java –32 kilobytes memory for runtime memory allocation –Restricted user interface –Low power, typically battery powered –Network connectivity, typically wireless, with low bandwidth and intermittent access

7Basics of J2ME CDC Packages CDC Package NameDescription java.iostandard I/O classes & interfaces java.langVM classes java.lang.refReference classes java.lang.reflectReflection classes & interfaces java.mathMath package java.netNetworking classes & interfaces java.securitySecurity classes & interfaces java.security.certSecurity certificate classes java.textText package java.utilstandard utility classes java..util.jarJAR utility classes java.util.zipZIP utility classes javax.microedition.ioCDC generic connection framework classes and interfaces

8Basics of J2ME CLDC Packages java.iostandard I/O classes & interfaces java.langVM classes java.utilstandard utility classes javax.microedition.ioCDC generic connection framework classes and interfaces

9Basics of J2ME The Java API’s J2SE CDC CLDC

10Basics of J2ME Profiles “To provide a complete runtime environment for a specific device category a configuration must be combined with a profile, a set of higher-level APIs that further define the application life-cycle model, the user interface, and access to device-specific properties. A profile supports a narrower category of devices within the framework of a chosen configuration. A widely adopted example is to combine CLDC with the Mobile Information Device Profile (MIDP) to provide a complete Java application environment for cell phones and other devices with similar capabilities.”

11Basics of J2ME CE00213-M Mobile Applications and Systems Basics of J2ME Profiles An extension to a configuration Provides libraries for a developer to write applications for a particular device –Mobile Information Device Profile (MIDP) defines API’s for user interface components, input & event handling, persistent storage, networking & timers, allowing for screen & memory limitation of mobile devices

12Basics of J2ME Java Virtual Machines –The JVM (java virtual machine) translates the class files into machine code for platform running the JVM –The JVM is also responsible for providing security, allocating& freeing memory & managing threads –For CDC the virtual machine is the same J2SE (re-engineered) –For CLDC the virtual machine is KVM (Kilobytes virtual machine) 128 Kbytes of memory for running the JVM & CLDC libraries must preserve it’s content when device is switched off (non volatile memory) 32 Kbytes during application runtime for allocation of objects (volatile memory or the “heap”)

13Basics of J2ME Mobile Information Device Profile (MIDP) MIDP is a set of API’s that allow developers to handle mobile device specific issues MIDP contains packages : –javax.microedition.lcdui Has classes to enable developers to construct user interfaces –javax.microedition.io Allows networking between midlets and other systems –javax.microedition.rms Allows local storage –javax.microedition.midlet Defines the midlet lifecycle

14Basics of J2ME Mobile Information Device Profile (MIDP) High level API’s –Textfields, lists, forms and images for programs such as e- commerce applications & basic user interfaces Low level API’s –Incorporate graphics & shapes at precise pixel locations, provides animation for games applications

15 Configuration for Small Devices - The Connected Limited Device Configuration (CLDC) Basics of J2ME

16Basics of J2ME References Beginning J2ME from Novice to Professional 3 rd edition 2005 –Sing Li, Jonathan Knudsen –Publisher Apress –ISBN Core J2ME Technology & MIDP 2002 –Muchow J.W –Publisher Sun microsystem –ISBN