Question

I read the following:

J2ME applications, unlike normal Java applications are preverified.

What exactly does the preverification of J2ME jar file mean? Is it something like checksum?

Answer 1

From here:

Answer Preverification is a new phase
in the development and deployment
cycle for Java applications designed
to run on the J2ME CLDC.
Preverification performs certain
checks on the Java bytecodes ahead of
runtime. If this first verification
pass is ok, the preverifier annotates
the classfiles (using standard Java
bytecode “attributes”, so that these
are still plain old Java bytecodes and
will be executable in VMs not aware of
the benefits of preverification), and
then saves the annotated class files
or passes them along to the next tool
in the compile chain.

When the KVM attempts to run execute a
J2ME CLDC-based application, it checks
the Java class files for these
preverification annotations. Proper
annotations in the class files
guarantee that certain compile-time
checks were made, and so the KVM can
pass through its own verfication and
security checks much faster and start
executing the application more
quickly.

Sun’s CLDC reference implementation
SDK includes the ‘preverify’ tool. You
use the tool after compiling your code
via javac (or your favorite Java
compiler). More information on
preverify is included in the CLDC
specification and in the developer
docs included with the CLDC SDK.