Java in A Small World

J2ME

• The Java[tm] 2 Platform, Micro Edition is a new edition of the Java 2 platform targeted at consumer electronics and embedded devices. J2ME consists of a virtual machine and a minimal layer of APIs targeted at providing only enough functionality to securely and safely download Java classes to a device and configure the Java environment.-
  Sun's Java 2 Micro Edition FAQ

J2ME Configurations

• Specifies Java Platform core technologies upon which one or more profiles may be layered.
• Configuration may include
  • VM (KVM, PersonalJava VM, Classic VM)
  • Core API (java.* packages, Optional Packages)
  • Defined through Java Community Process

Current Configurations

• Limited, Connected Device Configuration
  • those with 128-512 Kb of memory available for the Java environment (and applications)
• Connected Device Configuration
  • those with 512 Kb+ available for the Java environment (and applications)

J2ME Profiles

• A collection of Java technology based APIs that supplement a configuration to provide capabilities for a specific vertical market or device type.
• Profile may be usable on one or more Java 2 Platform Editions.
• Defined through Java Community Process
• Subject to compatibility test

PersonalJava

• PersonalJava technology provides a VM, a set of APIs, related tools, documentation, etc.
• Implementation tool for higher end consumer devices.
• What is used for developing devices within the Connected Device Configuration.

Embedded Java

• Implementation for devices with intermittent or no network connection and often no GUI.
• Implemented by vendors as a "black box" solution to allow vendors to customize and reduce APIs.
• Not a platform-base solution - dedicated functionality.

J2ME Review

• Configurations and profiles re specifications for J2ME
• PersonalJava, EmbeddedJava, and KVM are implementation tools for J2ME.

• Highly optimized Java virtual machine specifically designed for very resource-constrained consumer devices.
• Size: ~40K
• Requirements:
  • Processor: 16 bit/16 MHz or higher
  • Memory: 128-256 Kb of total memory

KVM Features

• Collections (Hashtable & Vector)
• Multithreading
• Garbage Collection
• Networking (limited to Sockets)
• Large data types (long, float and double)

Features Not Supported

• No support for Windows CE
• Determinism or other real time capabilities
• Jini
• AWT

KVM Versions

• Preview Version
  • Release at JavaOne '99
  • Not supported by Sun or Palm
• Early Access 0.1 (KVM DR4)
  • Did not include java.io or java.net packages
• Early Access 0.2 (KVM DR4.1)
  • Includes java.io and java.net packages

Installing KVM on Desktop

• The Palm OS[tm] Emulator (POSE) is software that emulates the hardware of the various models of Palm Computing[tm] platform devices. It is extremely valuable for writing, testing and debugging applications. -
  3Com's Palm Development Zone site

ROM

• OS for POSE
• Two ways to get a ROM
  • upload it form your Palm Pilot
  • get one from the Palm Development Zone
    • can get multiple versions (Palm III, V, VII)
    • can get ROM with debugging code

KVM Sample App.

• Install the KVM.prc and KVMClassDB.pdb on POSE
• Compile HelloWorld.java
• Make HelloWorld.prc
• Install on POSE and test

KJxfer

• Utility to add classes to the KJavaClassDB
• Cannot delete these files from the DB
• Cannot beam Java app. that depends on these new classes in DB
• Does not work with POSE

kAWT Project

• Port of the AWT toolkit to the KVM
• Size: ~230K (larger than KVM base)
• Slows down application
• But very cool