1. Java 2 Micro Edition (J2ME) and the world of java
J2ME - Lecture 8
Java 2 Micro Edition (J2ME) and the world of java
The Java 2 Platform, Micro Edition (J2ME) provides a flexible environment for applications running on consumer devices, such as mobile phones, PDAs, and TV set-top boxes, as well as a broad range of embedded devices.
J2ME includes Java virtual machines and a set of standard Java APIs
It includes flexible user interfaces, a robust security model, a broad range of built-in network protocols, and extensive support for networked and offline applications
Programming Mobile and Handheld Devices

2. The J2ME Architecture
The J2ME architecture comprises a variety of configurations, profiles, and optional packages that implementers and developers can choose from

3. J2ME Configurations and Profiles
Even within J2ME one size does not fit all
Configurations: Minimum libraries and JVM
Profiles: libraries for specific devices or markets
J2ME configurations
CLDC
CDC
J2ME profiles
MIDP
Foundation, Bluetooth, Personal, ...
Configurations and profiles defined by the Java Community ProcessSM

4. Configurations Configurations comprise
J2ME - Lecture 8
Configurations
Configurations comprise
a virtual machine
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)
Established and widely used
the Connected Device Configuration (CDC)
Next generation configuration *
* FUNCTION: PilotMain
* DESCRIPTION: This is the main entry point for the application.
* PARAMETERS: cmd - word value specifying the launch code.
* cmdPB - pointer to a structure that is associated with the launch code.
* launchFlags - word value providing extra information about the launch.
* RETURNED: Result of launch
As is usual in Palm applications, PilotMain calls AppStart, AppEventLoop and AppStop to do the work
Programming Mobile and Handheld Devices

5. J2ME - Lecture 8
Profiles
To provide a complete runtime environment for a specific device category a configuration must be combined with a profile
This is 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
Programming Mobile and Handheld Devices

6. J2ME - Lecture 8
Optional Packages
The J2ME platform can be extended by adding various optional packages to a technology stack that includes either CLDC or CDC and an associated profile.
Optional packages offer standard APIs for using both existing and emerging technologies such as database connectivity, wireless messaging, multimedia, Bluetooth, and web services.
Because optional packages are modular, developers can avoid carrying the overhead of unnecessary functionality by including only the packages an application actually needs.
Programming Mobile and Handheld Devices

7. J2ME - Lecture 8
Programming Mobile and Handheld Devices

8. Mobile Information Device Profile
J2ME - Lecture 8
Mobile Information Device Profile
The first J2ME profile
Targets devices implementing CLDC
Profile addresses:
Display toolkit, user input methods
Persistent data storage
Messaging( SMS, , etc), security and networking over wireless network connection
Programming Mobile and Handheld Devices

9. Related Technologies: Java Card™ Technology
J2ME - Lecture 8
Related Technologies: Java Card™ Technology
Specifies minimized subset of Java technology for GSM SIM cards, smart cards, Java rings, and other extremely constrained devices
Key benefits versus non-Java smart cards
Multiple applications per card
Post-issuance updates to apps on card
Programming Mobile and Handheld Devices

10. Related Technologies: EmbeddedJava™ Technology
J2ME - Lecture 8
Related Technologies: EmbeddedJava™ Technology
EmbeddedJava. technology is a program from Sun supporting development of dedicated-function embedded devices for a wide range of end uses
EmbeddedJava technology gives device manufacturers the ability to:
Configure the Java platform to leave out unneeded classes and VM features
Minimize resource requirements and cost for a deeply-embedded device
Optimize for devices with no GUI and intermittent (at best) networking
Keep APIs for their devices private
Programming Mobile and Handheld Devices

11. J2ME™: Connected Device Configuration
J2ME - Lecture 8
J2ME™: Connected Device Configuration
Connected Device Configuration (CDC)
Targeted for devices that have 2 MB or more total available memory
Memory dedicated to J2ME environment
More than 2MB ROM/Flash
More than 512 KB RAM
Network connectivity
Full Java 2 Virtual Machine specification
Programming Mobile and Handheld Devices

12. Example J2ME™ CDC Uses Wireless communicators High-end PDAs
J2ME - Lecture 8
Example J2ME™ CDC Uses
Wireless communicators
High-end PDAs
TV set-top boxes
Gateways
Automotive entertainment and navigation systems
Telecomm/Networking Equipment
Industrial Controllers
Programming Mobile and Handheld Devices

13. What Is CVM? Basis for J2ME CDC and profiles
J2ME - Lecture 8
What Is CVM?
Basis for J2ME CDC and profiles
Large VMs for desktops/servers don.t scale well to devices
Static and dynamic memory footprint too big
Not embeddable, ROMable, not portable
Implicit assumption of virtual memory
Native stack use, address range reservation
Implicit assumption of process model
Global variables, .system threads.
Programming Mobile and Handheld Devices

14. CVM features CVM supports all Java 2 Platform, version 1.3,
J2ME - Lecture 8
CVM features
CVM supports all Java 2 Platform, version 1.3,
VM features and libraries for security, weak references, JNI, RMI and JVMDI
CVM allows devices to map Java threads directly to native threads.
Can run Java classes out of ROM
Contains a precise memory system with advanced Garbage Collection features:
Small average GC pause times
Pluggable Garbage Collectors
Full separation of VM from memory system
Good JVM features
Device friendliness.
Easily re-targetable
Narrow porting interface
Almost entirely in C (except dynamic compiler)
~256KB with JNI, reflection, verification,.
Programming Mobile and Handheld Devices

15. J2ME Profiles Mobile Information Device Profile (MIDP)
J2ME - Lecture 8
J2ME Profiles
Mobile Information Device Profile (MIDP)
Profile for wireless devices implementing CLDC
J2ME Foundation Profile
Profile for non-GUI networked devices implementing CDC
J2ME Personal Basis, Personal, RMI Profiles
Basic graphics, next generation PersonalJava environment, and RMI support for CDC & Foundation Profile based devices
Programming Mobile and Handheld Devices

16. CDC APIs 􀀀 Defines minimum set of APIs for Java VM support
J2ME - Lecture 8
CDC APIs
􀀀 Defines minimum set of APIs for Java VM support
java.lang VM system classes (Object, Thread, etc.)
java.util.Underlying utilities
java.net.UDP Datagram and File URL
java.io.File
java.text.I18n support for Java VM error messages
java.security.Fine grain security and encryption for object serialization
Programming Mobile and Handheld Devices

17. CVM Sizes Today CVM only Natives only Porting layer only
J2ME - Lecture 8
CVM Sizes Today
CVM only
Static ROM + RAM req.= 258 KB
Natives only
Static ROM + RAM req.= 124 KB
Porting layer only
Static ROM + RAM req.= 28 KB
CVM+natives+porting_layer
Static ROM + RAM req.= 410 KB
Programming Mobile and Handheld Devices

18. Foundation Profile APIs
J2ME - Lecture 8
Foundation Profile APIs
Defines core set of Java platform functionality
No GUI
Subset of JDK 1.3
Completes full functionality from CDC
java.lang.Rounds out full java.lang.*(Compiler, UnknownError)
java.util.Adds full zip support, Timer, etc.
java.net.Adds TCP Socket and HTTP
java.io.Rounds out full java.io.* (Readers and Writers)
java.text.Full I18n (Annotation, Collator, Iterators, etc.)
java.security.Adds Code Signing and Certificates
Programming Mobile and Handheld Devices

19. CVM Sizes with Foundation Profile APIs
J2ME - Lecture 8
CVM Sizes with Foundation Profile APIs
CDC Java libraries (ROMized)
Static ROM + RAM req.= 1011 KB
Foundation Java libraries (ROMized)
Static ROM + RAM req.= 1564 KB
CDC TOTAL (CVM+natives+porting+libraries)
Static ROM + RAM req.= 1421 KB
Java libraries + natives for Foundation Profile
Static ROM + RAM req = 553 KB
Foundation TOTAL (CVM+natives+porting+libraries)
Static ROM + RAM req.= 1974 KB
Programming Mobile and Handheld Devices