Introduction to java 2 platform

8/6/2019 Introduction to java 2 platform

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Introduction to J2ME

Presented By:
http://www.sun.com/http://java.sun.com/http://java.sun.com/j2me/


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J2ME 2

Contents

Whats J2ME?

Java Editions

J2ME core concepts

Configurations (CLDC, CDC) Profiles (MIDP)

MIDP and MIDlets

Basic Classes API

Java Technology Carriers

Java Technology Handsets

Overall Evaluation


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J2ME 3

Introduction

Personalized and intelligent informationappliances are necessities in our life today.

Such appliances can be:

cell phones

two-way pagers

smart cards personal organizers

palmtops These appliances tend to be special-purpose,

limited-resource, network-connected devices.


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J2ME 4

Environment requirements

We need an environment which is adaptedfor constrained devices - devices that havelimitations on what they can do when

compared to standard desktop or servercomputers.

The constraints are: extremely limited memory

small screen sizes

alternative input methods

slow processors


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At the JavaOne Conference in June 1999,Sun Microsystems announced a new editionof the Java 2 platform: the Java 2 Micro

Edition (J2ME).

J2ME 5


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J2ME 6

Java Editions

Different devices have differentrequirements and different expectations ofJava.

One platform (solution) cannot address allthe market segments (web server, videogames etc.)

Users/developers want flexibility. Theywant to choose what they want to use andwhat they do not.


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J2ME 7

Java Editions

The Java 2 Platform is split into threeeditions.

Each edition provides a complete

environment for running Java-basedapplications, including the Java virtualmachine (VM) and runtime classes.

The three editions target different kinds ofapplications running on different kinds ofdevices.


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J2ME 8

Java Editions

Java2Standard Edition

(J2SE)

Java2Enterprise Edition

(J2EE)

Java2Micro Edition

(J2ME)

Java 2 Platform

Standard desktop &workstation applications

Heavy duty serversystems

Small & memoryconstrained devices


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J2ME 9

Java Editions

Each edition defines different sets ofclass libraries.

There are thousands of core J2SE

runtime classes, taking up to 10-20megabytesof space.

J2ME-based devices havefewer classes.

J2ME

J2SE

J2EE


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Java Family


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What is J2ME

J2ME is a family of specifications thatdefines various downsized versions of thestandard Java 2 platform; these downsizedversions can be used to program consumer

electronic devices ranging from cell phonesto highly capable Personal Data Assistants(PDAs), smart phones, and set-top boxes.

---J2ME in a Nutshell A Desktop Quick Reference

ByKim Topley


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J2ME 12

PersonalJava and EmbeddedJava

J2ME is not the first attempt at adaptingJava for constrained environments.

PersonalJava

EmbeddedJava


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Sun Microsystems Web sitedescribes J2ME this way:

. . . Java 2 Platform, Micro Edition is a highlyoptimized Java runtime environment

targeting a wide range of consumerproducts, including pagers, cellular phones,screenphones,digital set-top boxes and carnavigation systems.

J2ME 13


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J2ME 14

J2ME Core Concepts

J2ME is based on 3 core concepts:

Configurations

Profiles Optional packages


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J2ME Category

Principle: Different hardware corresponds different JVMs, hardware which base on CDC havepowerful JVMs, and hardware which base on CLDC have KVM to support.

J2ME Model
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J2ME 16

Configurations

A configuration is a complete Javaruntime environment, consisting of: Java virtual machine (VM) to execute

Java bytecode

Native code to interface to theunderlying system

Set of core Java runtime classes

To use a configuration, a device mustmeet certain minimum requirements.


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J2ME 17

Configurations

The set of core classes is normallyquite small and must be enhancedwith additional classes supplied byJ2ME profiles or by configurationimplementor.

Configurations do not define any user

interface classes.


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J2ME 18

Configurations

Configuration

CLDC CDC

Connected Limited

Device Configuration

Connected Device

Configuration


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Connected Device Configuration (CDC)

Device requirements: A connected device (CD)has a minimum 512KB of ROM, 256KB of RAM,32-bit processors, and some network

connection with limited bandwidth CDC is designed for "more powerful" wireless

devices like TV set-top boxes, car navigationsystems, and high-end PDAs.

CDC specifies that a full-featured Java VirtualMachine (JVM) (defined in J2EE) is supported


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Connected, Limited DeviceConfiguration (CLDC)

Covers mobile devices like mobile phones, PDAs,

pagers, and other "tiny" wireless devices

For smaller devices than CDC, with limited capacity

and network connection For devices with 160KB to 512 KB of memory

available for Java platform

For devices with limited power supply

Built on "scale-down" version of JVM called KVM

(Sun 'K Virtual Machine, with size in tens of

kilobytes, rather than JVM with tens of megabytes)


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J2ME 21

J2ME Core Concepts


Configurations

Profiles

Optional packages


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Profiles

Adds domain-specific classes to aconfiguration: To fill in missing functionality

To support specific uses of a device Most profiles define user interface classes

for building interactive applications.

To use a profile, the device must meet the

minimum requirements of the underlyingconfiguration and of the profile.


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J2ME 23

Profiles

Profile

MIDP PDAP PPPBPFP

Mobile

Information

Device

Profile

Personal

Digital

Assistant

Profile

Foundation

Profile

Personal

Basis Profile

Personal

Profile


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J2ME 24

MIDP MID Profile

MIDP is targeted at a class of devicesknown as mobile information devices(MIDs).

Minimal characteristics of MIDs: Enough memory to run MIDP applications

Display of at least 96 X 56 pixels, eithermonochrome or color

A keypad, keyboard, or touch screen Two-way wireless networking capability


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J2ME 25

MIDP - Specification

The MIDP adds APIs to the basic APIs defined bythe CLDC. The new features include:

Support for application lifecycle management similarto the way applets are defined in J2SE.

Persistent storage of data.

HTTP-based network connectivity based on theCLDC's GCF.

Simple user interface support, with enough flexibility

to build games or business applications.


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MIDP - Specification

The MIDP specification is silent abouta number of things: No standard way to interface to the

device's phonebook, in order to initiatevoice calls.

How MIDP applications are loaded onto adevice and how they are activated ordeactivated.


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J2ME 27

MIDP Applications restrictions

Memory is a particularly scarce resource. The early Motorola J2ME-enabled phones limited

the size of an application to 50K. Some Nokia

phones limit them to even less, about 30K. MIDP 1.0 applications cannot share classes.

Placing part of the application in a web orapplication server (as a servlet, typically)

that the MIDP application calls is almost arequirement for anything serious.


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MIDP API(familiar packages)

java.io

java.lang

java.lang.ref

java.util


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MIDP API(no so familiar packages)

javax.microedition.io

javax.microedition.lcdui

javax.microedition.lcdui.game

javax.microedition.media

javax.microedition.media.control

javax.microedition.midlet

javax.microedition.pki javax.microedition.rms


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MIDP and MIDlets

MIDP enables application development with mobile, wireless-connected devices like cellular phones and two-way pagers

Main features of the supported devices: small displays limited input devices

limited local storage limited battery life limited CPU power

MIDlets: Small applications that run under the MIDP are called MIDlets A MIDlet is a Java application that uses the MIDP and the CLDC

In a mobile phone, application management software (AMS)controls start, stop and execute MIDlet (controls the entirelifecycle)

Device manufacturer provides the AMS Software


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MIDlet states


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MIDlets The heart of J2ME

Every application must extendjavax.microedition.midlet.MIDletclass to allow the application

management software to: control the MIDlet

be able to retrieve properties from the

application descriptor notify and request state changes


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J2ME 33

J2ME Core Concepts


Configurations

Profiles

Optional packages


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J2ME 34

Optional Packages

Set of APIs in support of additional,common behaviors.

Have specific dependencies on a particular

configuration and/or one or more profiles.

Examples of optional packages :

RMI Optional Package

Bluetooth Optional Package JDBC Optional Package


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J2ME 35

What it all means

"J2ME application" is an ambiguous term.

Configuration, profile and optionalpackages should be chosen.

CDC-based profiles make developmentsimpler due to J2SE-like APIs, but dont suitthe low-end devices.

CLDC-based profiles makes the

development task harder, especially whentrying to shrink the size of the applicationto run on many of the small devices.

C i


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Carriers

H d t


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Handsets

To date, over 250 different handset models from more than 40 manufacturershave been developed with Java technology, with more than 100 million of thesehandsets shipped worldwide.


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Overall Evaluation

Advantages Easy to learn Learning J2ME is like learning Java programs

Platform independent The layering architecture of the J2ME

programming model allows MIDlets(applications for mobile devices) to run on

different mobile devices (Java systems). Build on top of an operating system and All lower levels components are hided by the

OS


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Overall Evaluation

Integration with other Javacomponents Can build complex mobile applications

using with least effort by integration withother Java components

Good for security-oriented applications,which use cryptographic classes

Can build wireless Internet applications


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Overall Evaluation

Limitations

Accessing device resources

Multimedia applications

Performance-intensive applications


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Overall Evaluation

There are more than 2.1 billion Java MEenabled mobile phones and PDAs, but it isbecoming old technology as it is not used

on any of today's newest mobile platforms(eg iPhone, Android, Windows Phone 7,MeeGo, BlackBerry's new QNX).


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J2ME 42

Getting Started

1st step: Download suns J2MEWireless Toolkit from:http://java.sun.com/products/j2mewtool

kit/download-2_1.html

2nd step:Make sure you have J2SESDK installed

3rd step: Install the J2ME Toolkit.


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Thanks

Documents

Introduction to java 2 platform