1. J2ME
Java 2 Micro Edition
Don Law

2. 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
slide 2

3. 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)
slide 3

4. 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
slide 4

5. Advantages of Java - Exceptions
method level 4
method level 3
this method can catch
FileNotFound and hide it
from method at level 4
method level 2
this method can throw
FileNotFound if it doesn't want
to handle it
Exeption FileNotFound
Name, stack trace, reason, error code, etc.
method level 1
throws
slide 5

6. Advantages of Java - Packages
Application
file subsystem
package
networking
package
nvram
package
CleanUp
CleanUp
CleanUp
slide 6

7. Advantages of Java - Automatic dependencies
repeat.c
caller.c
#include <stdio.h>
#include "repeat.h"
main() {
print("Repetition\n");
repeat("Copy me ", 5);
printf("\n"); }
#include <stdio.h>
void repeat(char *s, int count) {
int i;
for (i=0; i<count; i++) {
printf("%s", s); }
repeat.h
void repeat(char *s, int count);
slide 7

8. Advantages of Java - Automatic dependencies
caller.java
class caller {
public static void main(String[] args) {
System.out.println("Repetition");
repeat R = new repeat();
R.repeat("Copy me ", 5);
System.out.println(""); }
repeat.java
class repeat {
public void repeat(String s, int count) {
int i;
for (i=0; i<count; i++) {
System.out.print(s); }
javac *.java
slide 8

9. Advantages of Java -Casting adds checks
cast.c
#include <stdio.h>
#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; }
slide 9

10. 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);
"New float value is " + newf); }
increm.java
class increm {
public int increm(Object o) {
Integer i;
i = (Integer) o;
return i.intValue() + 1; }
slide 10

11. Advantages of Java -Casting adds checks
cast.c output
Let's cast
New int value is 6
New float value is
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.java:5)
at cast.main(cast.java:13)
slide 11

12. J2ME - Micro Edition What is different?
JVM
KVM
Java Card VM
graphic is from
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.
slide 12

13. 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.*
New addition:
javax.microedition.*
slide 13

14. J2ME - Micro Edition (CLDC) classes
ArrayIndexOutOfBoundsException IOException
ArrayStoreException ISO8859_1_Reader
Boolean ISO8859_1_Writer
Byte Long
ByteArrayInputStream Math
ByteArrayOutputStream NegativeArraySizeException
Calendar NetworkConnectionBase
CalendarImpl NoSuchElementException
Character NullPointerException
Class NumberFormatException
ClassCastException Object
ClassNotFoundException OutOfMemoryError
ConnectionBase OutputStream
ConnectionNotFoundException OutputStreamWriter
Connector PrintStream
DatagramObject Protocol
DatagramObject Random
DataInputStream Reader
DataOutputStream Runtime
Date RuntimeException
DateParser SecurityException
Default_Reader Short
Default_Writer Stack
DefaultCaseConverter StreamReader
EmptyStackException StreamWriter
EOFException String
Error StringBuffer
Exception StringIndexOutOfBoundsException
GeneralBase System
Hashtable Thread
Helper Throwable
IllegalAccessException TimeZone
IllegalArgumentException TimeZoneImpl
IllegalMonitorStateException TimeZoneImplementation
IllegalThreadStateException UniversalFilterInputStream
IndexOutOfBoundsException UniversalFilterOutputStream
InputStream UnsupportedEncodingException
InputStreamReader UTFDataFormatException
InstantiationException Vector
Integer VirtualMachineError
InterruptedException Writer
InterruptedIOException
slide 14

15. 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
slide 15

16. 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
slide 16

17. 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
slide 17

18. Resources
These slides are available for download from the Salient web site.
Click on Resources button
slide 18