Basics of J2ME

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Basics of J2ME
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Basics of J2ME

• Objectives
• Understand the different java APIs and how the
  mobile edition APIs fit in
• Understand what a mobile configuration and
  profile is.

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Basics of J2ME

• Quote from Sun
• The Micro Edition of the Java 2 Platform
  provides an application environment that
  specifically addresses the needs of commodities
  in the vast and rapidly growing consumer and
  embedded space, including mobile phones, pagers,
  personal digital assistants, set-top boxes, and
  vehicle telematics systems

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Basics of J2ME showing various editions
Java 2 Enterprise Edition (J2EE)
Java 2 Standard Edition (J2SE)
MIDP
Profile Level
CDC
CLDC
Configuration Level
Java Virtual Machine
KVM
Java 2 Micro Edition (J2ME)
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The Java Platform
Sourcehttp//java.sun.com/javame/technology/index
.jsp
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Basics of J2ME

• 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).

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Basics 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

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CDC Packages

• CDC Package Name Description
• java.io standard I/O classes interfaces
• java.lang VM classes
• java.lang.ref Reference classes
• java.lang.reflect Reflection classes
  interfaces
• java.math Math package
• java.net Networking classes interfaces
• java.security Security classes interfaces
• java.security.cert Security certificate classes
• java.text Text package
• java.util standard utility classes
• java..util.jar JAR utility classes
• java.util.zip ZIP utility classes
• javax.microedition.io CDC generic connection
  framework
• classes and interfaces

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CLDC Packages

• java.io standard I/O classes interfaces
• java.lang VM classes
• java.util standard utility classes
• javax.microedition.io CDC generic connection
  framework
• classes and interfaces

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The Java APIs
J2SE
CDC
CLDC
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Basics 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.

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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
  APIs for user interface components, input
  event handling, persistent storage, networking
  timers, allowing for screen memory limitation
  of mobile devices

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Basics 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 its content when device
  is switched off (non volatile memory)
• 32 Kbytes during application runtime for
  allocation of objects (volatile memory or the
  heap)

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Mobile Information Device Profile (MIDP)

• MIDP is a set of APIs 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

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Mobile Information Device Profile (MIDP)

• High level APIs
• Textfields, lists, forms and images for programs
  such as e-commerce applications basic user
  interfaces
• Low level APIs
• Incorporate graphics shapes at precise pixel
  locations, provides animation for games
  applications

Download the J2ME wireless toolkit from
http//java.sun.com/products/j2mewtoolkit/download
-2_1.html
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Configuration for Small Devices - The Connected
Limited Device Configuration (CLDC)
Sourcehttp//java.sun.com/javame/technology/index
.jsp
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References

• Beginning J2ME from Novice to Professional 3rd
  edition 2005
• Sing Li, Jonathan Knudsen
• Publisher Apress
• ISBN 1-59059-479-7
• Core J2ME Technology MIDP 2002
• Muchow J.W
• Publisher Sun microsystem
• ISBN 0-13-066911-3