Java2 MicroEdition-J2ME

1. Java 2 Micro Edition (J2ME)
or
Java ME
Rohan Chandane
rohan.chandane@indiatimes.com
These notes are created by me, Rohan Chandane as learning material while pursuing MSc (CA) from SICSR. (CC) 2005-07

2. Basics
 Sun's version of Java aimed at
machines
 with limited hardware resources
(PDAs, Cell Phones, Embedded devices)
 with less memory (128KB of RAM)
 with processors less powerful than desktop
and server machines

3. Continued…
 A highly optimized Java runtime
environment
 The collection of virtual machines, APIs
and related elements that provide Java to
handheld and embedded computing
devices

4. Components of J2ME
 There are different variation in devices
in terms of
 Memory
 Processor
 To support these differences, J2ME
introduced the concept of
 Configurations
 Profiles
 Optional Package

5. Continued…
 Configurations
 Provide the base functionality
 For a particular range of devices that share
similar characteristics like
 Memory
 Network Connectivity
 Two J2ME configurations
 Connected Limited Device Configuration (CLDC)
 Connected Device Configuration (CDC)

6. Continued…
 Profiles
 Profiles refers to APIs for a specific domain
 That sits on top of a given configuration
 Providing
 Specific features
 Application life-cycle model
 User interface
 Capabilities
 Persistent storage
 Access to device

7. Continued…
 Each profile define particular device
 Cell phones
 PDAs
 Microwave ovens, etc.
 In short, Profile is minimum set of class
libraries required for the particular type of
device
 Widely adopted profile
 Mobile Information Device Profile (MIDP)

8. Continued…
 We can use more than one profile at a
time
 Provided that the virtual machine and device
supports the functionality for the additional
profile

9. Continued…
 Optional Package
 Extend the J2ME platform by adding extra
functionality
 Offer standard APIs for using both existing
and emerging technologies like
 Database connectivity
 Wireless messaging
 Multimedia
 3D graphics
 Web Services

10. The J2ME Platform

11. Details about Configuration
 Connected Limited Device Configuration
(CLDC)
 For small wireless devices with intermittent
(periodic) network connections
 Mobile phones
 Personal digital assistants
 Mobile Information Device Profile (MIDP),
which is based on CLDC

12. Continued…
 Typical characteristics of a device that
implements the CLDC
 128 KB of memory for running Java programs
 32 KB of memory for run time memory
allocation
 16-/32-bit RISC/CISC processor
 A limited user interface
 Runs on battery power
 Some form of wireless network connection, low
bandwidth

13. Continued…
 Support in CLDC
 Support floating point math
 CLDC 1.0 specification – does not support
 CLDC 1.1 specification – does support

14. Continued…
 Connected Device Configuration (CDC)
 For larger devices in terms of memory and
processing power with robust network
connections
 Set-top boxes
 Internet appliances
 Embedded servers
 Foundation Profile extends CDC
 It provides core APIs shared with Java SE

15. Continued…
 Typical characteristics of a device that
implements the CDC
 512 kilobytes (minimum) memory for running
Java programs
 256 kilobytes (minimum) for run time memory
allocation
 Network connectivity, possibly persistent, and
high-bandwidth

16. Details about Profiles
 Profiles have been defined for J2ME
 Built upon CLDC
 Mobile Information Device Profile (MIDP)
 KJava
 Built upon CDC
 Foundation Profile
 Personal Profile

17. Continued…
 Mobile Information Device Profile (MIDP)
 APIs built on top of the CLDC configuration
 Defines following APIs for cellular devices
 User Interface Components
 Input and Event handling
 Persistent storage
 Networking and timers
 Common, industry-standard profile
 Not dependent on a specific vendor

18. Continued…
 Versions of the MIDP specification
 Version 1.0
 Original specification
 Version 2.0
 Addressed many of the shortcomings
 Backwards compatible with version 1.0

19. Continued…
 MIDP contains the following packages
 Core CLDC packages
 java.lang
 java.io
 java.util
 MIDP-specific packages
 javax.microedition.io
 javax.microedition.lcdui
 javax.microedition.midlet
 javax.microedition.rms

20. Continued…
 KJava
 Sun's proprietary profile
 Built on top of the CLDC configuration
 Contains a Sun-specific API
 Which runs on the Palm OS
 It is not a standard J2ME package
 Main package is com.sun.kjava

21. Continued…
 Foundation Profile
 Intended for embedded and headless
devices
 For devices that have no user interface
 Routers
 Gateway devices
 There are other profiles, such as Personal
Profile, that are intended to run on top of
the Foundation profile

22. Continued…
 Personal Profile
 Personal Profile is the JavaME replacement
for PersonalJava
 Defines a minimal set of user interface
APIs

23. Java editions & Applications

24. JCP & JSR
 Configurations and Profiles are defined
by Java Community Process (JCP)
 JCP - Open industry working groups utilizing
Sun's Java Community Process Program
 This program is formed by an expert group
consisting of representatives from
participating companies

25. Continued…
 In this way industries can decide for
themselves what elements are necessary
to provide a complete solution targeted at
their industry
 Specifications for J2SE, J2EE and J2ME
are developed under the JCP

26. Continued…
 Specification begins life as a Java
Specification Request (JSR)
 JSR then passes through various stages
in the JCP before it is finalized
 Every JSR is assigned a number
 J2ME specifications are commonly
referred to by their JSR number

27. K Virtual Machine (KVM)
 For CDC
 The virtual machine has the same
specification as J2SE
 That is Java Virtual Machine (JVM)
 For CLDC
 Sun has developed a reference
implementation of a virtual machine,
known as the K Virtual Machine
 Simply known as KVM

28. Continued…
 The KVM is Sun's implementation of a
JVM that fits the guidelines of the CLDC

29. J2ME Architecture
quot;Genericquot; J2ME architecture MID Profile architecture