2. CLDC Devices Characteristics
• 160 - 512 kb total memory available for
java platform
• 16 bit / 32 bit processor
• low power consumption, often battery
powered
• intermitten network connectivity (often
wireless), limited bandwith
3. Hardware Requirements
• CLDC doesnt have specific hardware
requirements
• Minimal memory requirements :
• 128 kb - for running the JVM and CLDC libraries.
This memory must preserve its content, even
when the device is powered off. (Nonvolatile
memory)
• 32 kb - available during application runtime for
allocation of objects. (Volatile memory / heap)
4. Software Requirements
• The Operating System must be able to
running JVM and managing Java
applications on the device including :
Select and launch application
Remove application
6. Java Language for CLDC
• CLDC doesn’t support floating point type.
(double and float)
• CLDC doesn’t support finalize()
method.
• CLDC only support limited set of
Exception classes for error handling.
7. Java Virtual Machine for CLDC
• JVM doesn’t support floating point operation.
• JVM doesn’t support native interface and native
method invocation.
• Reflection is not available.
• JVM must implement the classloader.
• finalize() method is not available.
• JVM doesn’t suport ThreadGroup class.
• JVM doesn’t support weak references.
8. Weak References
• Garbage collector recognizes that an
object is being referenced, yet the object is
still a candidate for garbage collection.
9. Security Handling
• Any devices running Java application will
need protection from malicious codes that
may access system information or
resources.
• This “Low Level” protection is
implemented through class file verification.
10. CLDC Class File Verification
• Class file verification is done in 2 steps in
CLDC.
• 1st Step is pre-verification.
• 2nd Step is in-device verification.
11. Pre-Verification
• Pre-verification :
• A software program is run to insert additional
attributes into the class file.
• Class file will be approximately 5% larger after
pre-verification.
• Done as part of development process or before
a class file is loaded on a device.
• A "Stack Maps" is added to the class file,
describing what variables and operands are art
of the interpreter stack space.
12. In-Device Verification
• In-Device verification :
• Once a device loads a pre-verified class file, the
in-device verifier runs through each instruction.
• There are several checks done to validate the
code.
• At any point the verifier can report and reject the
class file.
• Code verifier program for KVM is in the range of
10kb and less than 100 bytes of heap space
required.
25. Reference
• Core J2ME Technology and MIDP. John
W. Muchow. Prentice Hall PTR, 2002.
• Enterprise J2ME: Developing Mobile
Java Applications. Michael Juntao Yuan.
Prentice Hall PTR, 2003.
• J2ME in A Nutshell. Kim Topley. Oreilly,
2002.
• Wireless J2ME Platform Programming.
Vartan Piroumian. Prentice Hall, 2002.
