J2ME

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J2ME
Java 2 Micro Edition Don Law
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Outline
1. Java background A. Origin of Java B.
Advantages Java brings 2. J2ME A. Differences
between J2ME and Standard Edition (security,
classes) B. The KVM 3. J2ME industry
acceptance 4. Write once run anywhere? 5. J2ME
examples A. On a Linux box B. On a Motorola cel
phone C. On a TINI chip
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Java background
Born in a Menlo Park closet at Sun in 1991 Grew
out of Sun Microsystems Reasearch
Development Oak - a language for 7
development Integrated into browsers - WebRunner
then Netscape Only been productized since
1995 Today 750 user groups 2,500,000
developers 2200 commercial appliations 56 of
universities require learning Java Overtake of
C is expected next year (2003)
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Advantages of Java
Tools like Forte now known as SunONE
Studio community edition is free The Java
Tutorial Object oriented features built
in Encapsulation, inheritance, etc. Modern
language Exceptions Packages Automatic
dependencies Pointers are encapsulated under
objects Threads are part of the
language Casting adds checks instead of
suppressing Compiler does more work for you See
also http//www.firststep.com.au/jlc/javacc/plusse
s.html
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Advantages of Java - Exceptions
method level 4
this method can catch FileNotFound and hide
it from method at level 4
method level 3
this method can throw FileNotFound if it doesn't
want to handle it
method level 2
Exeption FileNotFound Name, stack trace, reason,
error code, etc.
method level 1
throws
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Advantages of Java - Packages
Application
nvram package
networking package
file subsystem package
CleanUp
CleanUp
CleanUp
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Advantages of Java -Automatic dependencies
repeat.c
caller.c
include ltstdio.hgt include "repeat.h" main()
print("Repetition\n") repeat("Copy me ",
5) printf("\n")
include ltstdio.hgt void repeat(char s, int
count) int i for (i0 iltcount i)
printf("s", s)
repeat.h
void repeat(char s, int count)
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Advantages of Java -Automatic dependencies
caller.java
class caller public static void
main(String args) System.out.println("Repeti
tion") repeat R new repeat() R.repeat("Cop
y me ", 5) System.out.println("")
repeat.java
class repeat public void repeat(String s,
int count) int i for (i0 iltcount
i) System.out.print(s)
javac .java
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Advantages of Java -Casting adds checks
cast.c
include ltstdio.hgt include "increm.h" main()
int ok 5 float notok 5.1 int
newi float newf printf("Let's
cast\n") newi increm(ok) printf("New
int value is i\n", newi) newf
increm(notok) printf("New float value is
f\n", newf)
increm.c
int increm(void o) int i int ptr
ptr (int ) o i ptr return i
1
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Advantages of Java -Casting adds checks
cast.java
class cast public static void main(String
args) Integer ok new Integer(5) Float
notok new Float(5.1) int newi float
newf System.out.println("Let's
cast") increm I new increm() newi
I.increm(ok) System.out.println( "New int
value is " newi) newf I.increm(notok) Syst
em.out.println( "New float value is " newf)

increm.java
class increm public int increm(Object o)
Integer i i (Integer) o return
i.intValue() 1
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Advantages of Java -Casting adds checks
cast.c output
Let's cast New int value is 6 New float value is
1084437248.000000
cast.java output
Let's cast New int value is 6 Exception in thread
"main" java.lang.ClassCastException
java.lang.Float at increm.increm(increm.java5)
at cast.main(cast.java13)
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J2ME - Micro Edition
What is different?
Java Card VM
KVM
JVM
graphic is from http//java.sun.com/java2/whatis
scaled down - about 1460 classes in J2SE to about
83 in CLDC security removed (class validation,
HTTPS, etc.) profiles assume you are not on a
regular computer no floating point, persistence,
or user interface components no JNI, reflection,
user class loaders, thread groups,
weak references, or finalization.
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J2ME - CLDC - KVM
Rewrite of the Java Virtual Machine Comfortable
on 16 bit CPUs KVM is about 50 Kbytes VM plus
libraries is about 128 KBytes
From J2SE java.lang. java.util. java.io. N
ew addition javax.microedition.
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J2ME - Micro Edition (CLDC) classes
ArrayIndexOutOfBoundsException
IOException ArrayStoreException
ISO8859_1_Reader Boolean
ISO8859_1_Writer Byte
Long ByteArrayInputStream
Math ByteArrayOutputStream
NegativeArraySizeException Calendar
NetworkConnectionBase Calen
darImpl
NoSuchElementException Character
NullPointerException Class
NumberFormatException Clas
sCastException
Object ClassNotFoundException
OutOfMemoryError ConnectionBase
OutputStream ConnectionNotFoundException
OutputStreamWriter Connector
PrintStream DatagramObject
Protocol DatagramObject
Random DataInputStream
Reader DataOutputStream
Runtime Date
RuntimeException DateParser
SecurityException Default_Reade
r Short Default_Writer
Stack DefaultCaseConverter
StreamReader EmptyStackExceptio
n StreamWriter EOFException
String Error
StringBuffer Exception
StringIndexOutOfBoundsExc
eption GeneralBase
System Hashtable
Thread Helper
Throwable IllegalAccessException
TimeZone IllegalArgumentException
TimeZoneImpl IllegalMonitorStateException
TimeZoneImplementation IllegalThreadStateExcept
ion UniversalFilterInputStream IndexOu
tOfBoundsException
UniversalFilterOutputStream InputStream
UnsupportedEncodingException Inp
utStreamReader
UTFDataFormatException InstantiationException
Vector Integer
VirtualMachineError InterruptedException
Writer InterruptedIOException
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J2ME acceptance
First devices out in Q4 of 2000 Gartner Group
J2ME will be leveraged by 70 of smart phones
and PDAs by 2004 Big presense in wireless and
mobile Canal, Fujitsu, Hitachi,
Mitsubishi, Motorola, NEC, Nokia, OnStar, Palm,
Philips, Sharp, Siemens, Sony
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J2ME Can I still write once run anywhere?
bytecodes are bytecodes embedded tends to be
more platform-specific especially persisitence,
comminication, etc. loading and installation is
not standard writing within configurations
(CLDC/CLC) and profiles (MIDP) preserves
portability distribute a JAR without source that
is usable on J2ME platforms
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J2ME Examples
On a Linux box or anyplace GCC works On a
Motorola cel phone CLDC compliant serial
port network attached On a TINI chip Tiny
Internet Network Interface by Dallas
Semiconductor on 72 pin SIMM, 1MG persistent
RAM JVM, TCP/IP stack, unix-like shell 2x
RS-232, 10baseT, 1-Wire, 2x CAN
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Resources
These slides are available for download from the
Salient web site. http//www.salientsoftware.net
Click on Resources button
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