Embedded Java - JavaTech: An Introduction to Scientific and Technical Computing with Java - page 654

JVM used in J2SE, it monitors a program's performance dynamically and it
compiles frequently invoked methods (i.e. “hotspots”) into native instructions.
CDC platforms provide sufficient resources to allow for a JVM that meets all
of the official specifications [4]. Sun provides a reference JVM called the CDC
Hotspot Implementation (formerly called CVM) that provides the full J2SE specs,
but it doesn't implement all of the acceleration techniques of the J2SE Hotspot
and is optimized for a limited resource environment.
24.3.2 J2ME profiles
A profile expands a configuration so that it works for a specialized application:
Mobile Information Device Profile (MIDP) - this profile adds classes to the CLDC
to provide for networking, graphical user interfaces, and local storage. It is aimed at
wireless systems, especially cell phones, and allows for the downloading of MIDlets,
which are similar to applets but load and run on wireless platforms that are limited to
the CLDC capabilities. There are two versions of MIDP - version 1.0 and 2.0. The
latter adds numerous enhancements including multimedia and game APIs and support
for HTTPS. Early implementations of MIDP 2.0 were built on top of a CLDC 1.0
base. Newer implementations are built on a CLDC 1.1 base. Thus there are devices
with CLDC 1.0/MIDP 1.0, devices with CLDC 1.0/MIDP 2.0, and devices with CLDC
1.1/MIDP 2.0.
Information Module Profile (IMP) - this subset of the MIDP also applies to wireless
systems but those with little or no graphical interface. It is intended for wireless access
to remote devices such as alarm systems, meteorological stations, electric meters, and
so forth.
Foundation profile - this profile for the CDC applies to systems such as printers and
embedded servers with no graphical interfaces. It only adds three packages dealing with
security tasks.
Personal profile -aCDC profile that provides for an AWT-based GUI. Intended for
high-end PDAs, smart phones, and other resource limited systems as compared to desk-
tops PCs.
Several other profiles are in development such as a PDA profile for CLDC that
is specialized for those devices. There is also an optional package for the CDC
that provides for a subset of the J2SE RMI classes to provide for distributed
computing with micro-devices.
24.4 Real-time Java
Some embedded applications, such as controlling a cell phone or a heart-lung
machine pump, require real-time programming so we provide a brief overview
of real-time Java here [5,6]. Real-time essentially means providing both periodic
services and responses to asynchronous demands within strictly enforced time